diff --git a/src/analyzer/blockanalyzer.cpp b/src/analyzer/blockanalyzer.cpp
index 45212e70..d36ffebb 100644
--- a/src/analyzer/blockanalyzer.cpp
+++ b/src/analyzer/blockanalyzer.cpp
@@ -36,12 +36,14 @@
 #include "analyzerbase.h"
 #include "fht.h"
 
-const int BlockAnalyzer::kHeight = 2;
-const int BlockAnalyzer::kWidth = 4;
-const int BlockAnalyzer::kMinRows = 3;       // arbitrary
-const int BlockAnalyzer::kMinColumns = 32;   // arbitrary
-const int BlockAnalyzer::kMaxColumns = 256;  // must be 2**n
-const int BlockAnalyzer::kFadeSize = 90;
+namespace {
+constexpr int kHeight = 2;
+constexpr int kWidth = 4;
+constexpr int kMinRows = 3;       // arbitrary
+constexpr int kMinColumns = 32;   // arbitrary
+constexpr int kMaxColumns = 256;  // must be 2**n
+constexpr int kFadeSize = 90;
+}  // namespace
 
 const char *BlockAnalyzer::kName = QT_TRANSLATE_NOOP("AnalyzerContainer", "Block analyzer");
 
diff --git a/src/analyzer/blockanalyzer.h b/src/analyzer/blockanalyzer.h
index 4dbabf36..df911d64 100644
--- a/src/analyzer/blockanalyzer.h
+++ b/src/analyzer/blockanalyzer.h
@@ -43,13 +43,6 @@ class BlockAnalyzer : public AnalyzerBase {
  public:
   Q_INVOKABLE explicit BlockAnalyzer(QWidget*);
 
-  static const int kHeight;
-  static const int kWidth;
-  static const int kMinRows;
-  static const int kMinColumns;
-  static const int kMaxColumns;
-  static const int kFadeSize;
-
   static const char *kName;
 
  protected:
diff --git a/src/collection/collectionfilterwidget.cpp b/src/collection/collectionfilterwidget.cpp
index c7bb8e56..e257374d 100644
--- a/src/collection/collectionfilterwidget.cpp
+++ b/src/collection/collectionfilterwidget.cpp
@@ -61,6 +61,10 @@
 #include "settings/collectionsettingspage.h"
 #include "settings/appearancesettingspage.h"
 
+namespace {
+constexpr int kFilterDelay = 500;  // msec
+}
+
 CollectionFilterWidget::CollectionFilterWidget(QWidget *parent)
     : QWidget(parent),
       ui_(new Ui_CollectionFilterWidget),
diff --git a/src/collection/collectionfilterwidget.h b/src/collection/collectionfilterwidget.h
index 3ae9fa90..2d010b92 100644
--- a/src/collection/collectionfilterwidget.h
+++ b/src/collection/collectionfilterwidget.h
@@ -51,8 +51,6 @@ class CollectionFilterWidget : public QWidget {
   explicit CollectionFilterWidget(QWidget *parent = nullptr);
   ~CollectionFilterWidget() override;
 
-  static const int kFilterDelay = 500;  // msec
-
   enum class DelayBehaviour {
     AlwaysInstant,
     DelayedOnLargeLibraries,
diff --git a/src/context/contextview.cpp b/src/context/contextview.cpp
index 5c8fc4b0..df2383ce 100644
--- a/src/context/contextview.cpp
+++ b/src/context/contextview.cpp
@@ -65,7 +65,9 @@
 #include "contextview.h"
 #include "contextalbum.h"
 
-const int ContextView::kWidgetSpacing = 50;
+namespace {
+constexpr int kWidgetSpacing = 50;
+}
 
 ContextView::ContextView(QWidget *parent)
     : QWidget(parent),
diff --git a/src/context/contextview.h b/src/context/contextview.h
index afea0d9f..ff53d11d 100644
--- a/src/context/contextview.h
+++ b/src/context/contextview.h
@@ -101,8 +101,6 @@ class ContextView : public QWidget {
   void AlbumCoverLoaded(const Song &song, const QImage &image);
 
  private:
-  static const int kWidgetSpacing;
-
   Application *app_;
   CollectionView *collectionview_;
   AlbumCoverChoiceController *album_cover_choice_controller_;
diff --git a/src/core/commandlineoptions.cpp b/src/core/commandlineoptions.cpp
index a3f422dc..fef154c3 100644
--- a/src/core/commandlineoptions.cpp
+++ b/src/core/commandlineoptions.cpp
@@ -46,7 +46,9 @@
 
 #include <getopt.h>
 
-const char *CommandlineOptions::kHelpText =
+namespace {
+
+constexpr char kHelpText[] =
     "%1: strawberry [%2] [%3]\n"
     "\n"
     "%4:\n"
@@ -83,7 +85,9 @@ const char *CommandlineOptions::kHelpText =
     "      --log-levels <levels>  %33\n"
     "      --version              %34\n";
 
-const char *CommandlineOptions::kVersionText = "Strawberry %1";
+constexpr char kVersionText[] = "Strawberry %1";
+
+}  // namespace
 
 CommandlineOptions::CommandlineOptions(int argc, char **argv)
     : argc_(argc),
diff --git a/src/core/commandlineoptions.h b/src/core/commandlineoptions.h
index c289ab13..0cfc98da 100644
--- a/src/core/commandlineoptions.h
+++ b/src/core/commandlineoptions.h
@@ -41,9 +41,6 @@ class CommandlineOptions {
  public:
   explicit CommandlineOptions(int argc = 0, char **argv = nullptr);
 
-  static const char *kHelpText;
-  static const char *kVersionText;
-
   // Don't change the values or order, these get serialised and sent to
   // possibly a different version of Strawberry
   enum class UrlListAction {
diff --git a/src/core/deletefiles.cpp b/src/core/deletefiles.cpp
index 3983098b..739dfcec 100644
--- a/src/core/deletefiles.cpp
+++ b/src/core/deletefiles.cpp
@@ -34,7 +34,9 @@
 #include "deletefiles.h"
 #include "musicstorage.h"
 
-const int DeleteFiles::kBatchSize = 50;
+namespace {
+constexpr int kBatchSize = 50;
+}
 
 DeleteFiles::DeleteFiles(SharedPtr<TaskManager> task_manager, SharedPtr<MusicStorage> storage, const bool use_trash, QObject *parent)
     : QObject(parent),
diff --git a/src/core/deletefiles.h b/src/core/deletefiles.h
index b1c117de..4bd31914 100644
--- a/src/core/deletefiles.h
+++ b/src/core/deletefiles.h
@@ -41,8 +41,6 @@ class DeleteFiles : public QObject {
   explicit DeleteFiles(SharedPtr<TaskManager> task_manager, SharedPtr<MusicStorage> storage, const bool use_trash, QObject *parent = nullptr);
   ~DeleteFiles() override;
 
-  static const int kBatchSize;
-
   void Start(const SongList &songs);
   void Start(const QStringList &filenames);
 
diff --git a/src/core/songloader.cpp b/src/core/songloader.cpp
index 5d6977f4..fb8e42f0 100644
--- a/src/core/songloader.cpp
+++ b/src/core/songloader.cpp
@@ -62,8 +62,11 @@
 #  include "device/cddasongloader.h"
 #endif
 
+namespace {
+constexpr int kDefaultTimeout = 5000;
+}
+
 QSet<QString> SongLoader::sRawUriSchemes;
-const int SongLoader::kDefaultTimeout = 5000;
 
 SongLoader::SongLoader(SharedPtr<CollectionBackendInterface> collection_backend, const SharedPtr<Player> player, QObject *parent)
     : QObject(parent),
diff --git a/src/core/songloader.h b/src/core/songloader.h
index 5ccceae5..31eb7306 100644
--- a/src/core/songloader.h
+++ b/src/core/songloader.h
@@ -68,8 +68,6 @@ class SongLoader : public QObject {
     BlockingLoadRequired
   };
 
-  static const int kDefaultTimeout;
-
   const QUrl &url() const { return url_; }
   const SongList &songs() const { return songs_; }
 
diff --git a/src/core/windows7thumbbar.cpp b/src/core/windows7thumbbar.cpp
index bbb354de..e784cacf 100644
--- a/src/core/windows7thumbbar.cpp
+++ b/src/core/windows7thumbbar.cpp
@@ -37,8 +37,10 @@ extern HICON qt_pixmapToWinHICON(const QPixmap &p);
 #include "core/logging.h"
 #include "windows7thumbbar.h"
 
-const int Windows7ThumbBar::kIconSize = 16;
-const int Windows7ThumbBar::kMaxButtonCount = 7;
+namespace {
+constexpr int kIconSize = 16;
+constexpr int kMaxButtonCount = 7;
+}  // namespace
 
 Windows7ThumbBar::Windows7ThumbBar(QWidget *widget)
     : QObject(widget),
diff --git a/src/core/windows7thumbbar.h b/src/core/windows7thumbbar.h
index 43fcf91c..078709c0 100644
--- a/src/core/windows7thumbbar.h
+++ b/src/core/windows7thumbbar.h
@@ -39,9 +39,6 @@ class Windows7ThumbBar : public QObject {
   // Creates a list of buttons in the taskbar icon for this window.
   explicit Windows7ThumbBar(QWidget *widget = nullptr);
 
-  static const int kIconSize;
-  static const int kMaxButtonCount;
-
   // You must call this in the parent widget's constructor before returning to the event loop.  If an action is nullptr it becomes a spacer.
   void SetActions(const QList<QAction*> &actions);
 
diff --git a/src/covermanager/albumcoverloader.cpp b/src/covermanager/albumcoverloader.cpp
index f4dd1833..e1f4abca 100644
--- a/src/covermanager/albumcoverloader.cpp
+++ b/src/covermanager/albumcoverloader.cpp
@@ -46,6 +46,10 @@
 
 using std::make_shared;
 
+namespace {
+constexpr int kMaxRedirects = 3;
+}
+
 AlbumCoverLoader::AlbumCoverLoader(QObject *parent)
     : QObject(parent),
       network_(new NetworkAccessManager(this)),
diff --git a/src/covermanager/albumcoverloader.h b/src/covermanager/albumcoverloader.h
index 73814099..52806c5c 100644
--- a/src/covermanager/albumcoverloader.h
+++ b/src/covermanager/albumcoverloader.h
@@ -123,7 +123,6 @@ class AlbumCoverLoader : public QObject {
   void LoadRemoteImageFinished(QNetworkReply *reply, AlbumCoverLoader::TaskPtr task, const AlbumCoverLoaderResult::Type result_type, const QUrl &cover_url);
 
  private:
-  static const int kMaxRedirects = 3;
   SharedPtr<NetworkAccessManager> network_;
   bool stop_requested_;
   QMutex mutex_load_image_async_;
diff --git a/src/device/devicedatabasebackend.cpp b/src/device/devicedatabasebackend.cpp
index 9d3e44eb..2256d4a2 100644
--- a/src/device/devicedatabasebackend.cpp
+++ b/src/device/devicedatabasebackend.cpp
@@ -38,7 +38,9 @@
 #include "core/scopedtransaction.h"
 #include "devicedatabasebackend.h"
 
-const int DeviceDatabaseBackend::kDeviceSchemaVersion = 5;
+namespace {
+constexpr int kDeviceSchemaVersion = 5;
+}
 
 DeviceDatabaseBackend::DeviceDatabaseBackend(QObject *parent)
     : QObject(parent),
diff --git a/src/device/devicedatabasebackend.h b/src/device/devicedatabasebackend.h
index bdea60cc..8c4e8690 100644
--- a/src/device/devicedatabasebackend.h
+++ b/src/device/devicedatabasebackend.h
@@ -56,8 +56,6 @@ class DeviceDatabaseBackend : public QObject {
   };
   using DeviceList = QList<Device>;
 
-  static const int kDeviceSchemaVersion;
-
   void Init(SharedPtr<Database> db);
   void Close();
   void ExitAsync();
diff --git a/src/engine/chromaprinter.cpp b/src/engine/chromaprinter.cpp
index 03cfc2a0..1a4f7f43 100644
--- a/src/engine/chromaprinter.cpp
+++ b/src/engine/chromaprinter.cpp
@@ -43,10 +43,12 @@
 using u_int32_t = unsigned int;
 #endif
 
-static const int kDecodeRate = 11025;
-static const int kDecodeChannels = 1;
-static const int kPlayLengthSecs = 30;
-static const int kTimeoutSecs = 10;
+namespace {
+constexpr int kDecodeRate = 11025;
+constexpr int kDecodeChannels = 1;
+constexpr int kPlayLengthSecs = 30;
+constexpr int kTimeoutSecs = 10;
+}  // namespace
 
 Chromaprinter::Chromaprinter(const QString &filename)
     : filename_(filename),
diff --git a/src/engine/ebur128analysis.cpp b/src/engine/ebur128analysis.cpp
index ec75dcf8..19cb113e 100644
--- a/src/engine/ebur128analysis.cpp
+++ b/src/engine/ebur128analysis.cpp
@@ -47,10 +47,10 @@
 
 using std::unique_ptr;
 
-static const int kTimeoutSecs = 60;
-
 namespace {
 
+constexpr int kTimeoutSecs = 60;
+
 struct ebur128_state_deleter {
   void operator()(ebur128_state *p) const { ebur128_destroy(&p); };
 };
diff --git a/src/engine/gstengine.cpp b/src/engine/gstengine.cpp
index 7ce63d79..46ebf33c 100644
--- a/src/engine/gstengine.cpp
+++ b/src/engine/gstengine.cpp
@@ -64,21 +64,24 @@ using std::make_shared;
 
 const char *GstEngine::kAutoSink = "autoaudiosink";
 const char *GstEngine::kALSASink = "alsasink";
-const char *GstEngine::kOpenALSASink = "openalsink";
-const char *GstEngine::kOSSSink = "osssink";
-const char *GstEngine::kOSS4Sink = "oss4sink";
-const char *GstEngine::kJackAudioSink = "jackaudiosink";
-const char *GstEngine::kPulseSink = "pulsesink";
-const char *GstEngine::kA2DPSink = "a2dpsink";
-const char *GstEngine::kAVDTPSink = "avdtpsink";
-const char *GstEngine::InterAudiosink = "interaudiosink";
-const char *GstEngine::kDirectSoundSink = "directsoundsink";
-const char *GstEngine::kOSXAudioSink = "osxaudiosink";
-const char *GstEngine::kWASAPISink = "wasapisink";
-const int GstEngine::kDiscoveryTimeoutS = 10;
-const qint64 GstEngine::kTimerIntervalNanosec = 1000 * kNsecPerMsec;  // 1s
-const qint64 GstEngine::kPreloadGapNanosec = 8000 * kNsecPerMsec;     // 8s
-const qint64 GstEngine::kSeekDelayNanosec = 100 * kNsecPerMsec;       // 100msec
+
+namespace {
+constexpr char kOpenALSASink[] = "openalsink";
+constexpr char kOSSSink[] = "osssink";
+constexpr char kOSS4Sink[] = "oss4sink";
+constexpr char kJackAudioSink[] = "jackaudiosink";
+constexpr char kPulseSink[] = "pulsesink";
+constexpr char kA2DPSink[] = "a2dpsink";
+constexpr char kAVDTPSink[] = "avdtpsink";
+constexpr char InterAudiosink[] = "interaudiosink";
+constexpr char kDirectSoundSink[] = "directsoundsink";
+constexpr char kOSXAudioSink[] = "osxaudiosink";
+constexpr char kWASAPISink[] = "wasapisink";
+constexpr int kDiscoveryTimeoutS = 10;
+constexpr qint64 kTimerIntervalNanosec = 1000 * kNsecPerMsec;  // 1s
+constexpr qint64 kPreloadGapNanosec = 8000 * kNsecPerMsec;     // 8s
+constexpr qint64 kSeekDelayNanosec = 100 * kNsecPerMsec;       // 100msec
+}  // namespace
 
 GstEngine::GstEngine(SharedPtr<TaskManager> task_manager, QObject *parent)
     : EngineBase(parent),
diff --git a/src/engine/gstengine.h b/src/engine/gstengine.h
index c23930ce..5b7cbb95 100644
--- a/src/engine/gstengine.h
+++ b/src/engine/gstengine.h
@@ -56,6 +56,7 @@ class GstEngine : public EngineBase, public GstBufferConsumer {
   ~GstEngine() override;
 
   static const char *kAutoSink;
+  static const char *kALSASink;
 
   Type type() const override { return Type::GStreamer; }
   bool Init() override;
@@ -142,23 +143,6 @@ class GstEngine : public EngineBase, public GstBufferConsumer {
   static QString GSTdiscovererErrorMessage(GstDiscovererResult result);
 
  private:
-  static const char *kALSASink;
-  static const char *kOpenALSASink;
-  static const char *kOSSSink;
-  static const char *kOSS4Sink;
-  static const char *kJackAudioSink;
-  static const char *kPulseSink;
-  static const char *kA2DPSink;
-  static const char *kAVDTPSink;
-  static const char *InterAudiosink;
-  static const char *kDirectSoundSink;
-  static const char *kOSXAudioSink;
-  static const char *kWASAPISink;
-  static const int kDiscoveryTimeoutS;
-  static const qint64 kTimerIntervalNanosec;
-  static const qint64 kPreloadGapNanosec;
-  static const qint64 kSeekDelayNanosec;
-
   SharedPtr<TaskManager> task_manager_;
   GstStartup *gst_startup_;
   GstDiscoverer *discoverer_;
diff --git a/src/engine/gstenginepipeline.cpp b/src/engine/gstenginepipeline.cpp
index f16d7912..c36a7242 100644
--- a/src/engine/gstenginepipeline.cpp
+++ b/src/engine/gstenginepipeline.cpp
@@ -62,11 +62,15 @@
 #include "gstenginepipeline.h"
 #include "gstbufferconsumer.h"
 
-constexpr int GstEnginePipeline::kGstStateTimeoutNanosecs = 10000000;
-constexpr int GstEnginePipeline::kFaderFudgeMsec = 2000;
+namespace {
 
-constexpr int GstEnginePipeline::kEqBandCount = 10;
-constexpr int GstEnginePipeline::kEqBandFrequencies[] = { 60, 170, 310, 600, 1000, 3000, 6000, 12000, 14000, 16000 };
+constexpr int kGstStateTimeoutNanosecs = 10000000;
+constexpr int kFaderFudgeMsec = 2000;
+
+constexpr int kEqBandCount = 10;
+constexpr int kEqBandFrequencies[] = { 60, 170, 310, 600, 1000, 3000, 6000, 12000, 14000, 16000 };
+
+}  // namespace
 
 int GstEnginePipeline::sId = 1;
 
diff --git a/src/engine/gstenginepipeline.h b/src/engine/gstenginepipeline.h
index 03ef0eeb..aa4aaf09 100644
--- a/src/engine/gstenginepipeline.h
+++ b/src/engine/gstenginepipeline.h
@@ -193,11 +193,6 @@ class GstEnginePipeline : public QObject {
   void FaderTimelineFinished();
 
  private:
-  static const int kGstStateTimeoutNanosecs;
-  static const int kFaderFudgeMsec;
-  static const int kEqBandCount;
-  static const int kEqBandFrequencies[];
-
   // Using == to compare two pipelines is a bad idea, because new ones often get created in the same address as old ones.  This ID will be unique for each pipeline.
   // Threading warning: access to the static ID field isn't protected by a mutex because all pipeline creation is currently done in the main thread.
   static int sId;
diff --git a/src/equalizer/equalizer.cpp b/src/equalizer/equalizer.cpp
index b0f4b663..f79e70e6 100644
--- a/src/equalizer/equalizer.cpp
+++ b/src/equalizer/equalizer.cpp
@@ -49,9 +49,10 @@
 #include "equalizerslider.h"
 #include "ui_equalizer.h"
 
-const char *Equalizer::kGainText[] = { "60", "170", "310", "600", "1k", "3k", "6k", "12k", "14k", "16k" };
-
-const char *Equalizer::kSettingsGroup = "Equalizer";
+namespace {
+constexpr char kSettingsGroup[] = "Equalizer";
+const char *kGainText[] = { "60", "170", "310", "600", "1k", "3k", "6k", "12k", "14k", "16k" };
+}  // namespace
 
 Equalizer::Equalizer(QWidget *parent)
     : QDialog(parent),
diff --git a/src/equalizer/equalizer.h b/src/equalizer/equalizer.h
index b71a237b..48ba8bc5 100644
--- a/src/equalizer/equalizer.h
+++ b/src/equalizer/equalizer.h
@@ -44,9 +44,7 @@ class Equalizer : public QDialog {
   explicit Equalizer(QWidget *parent = nullptr);
   ~Equalizer() override;
 
-  static const int kBands = 10;
-  static const char *kGainText[kBands];
-  static const char *kSettingsGroup;
+  static constexpr int kBands = 10;
 
   struct Params {
     Params();
diff --git a/src/lyrics/lyricsfetcher.cpp b/src/lyrics/lyricsfetcher.cpp
index ab3e0ff3..021e1b6c 100644
--- a/src/lyrics/lyricsfetcher.cpp
+++ b/src/lyrics/lyricsfetcher.cpp
@@ -35,7 +35,9 @@
 
 using namespace std::chrono_literals;
 
-const int LyricsFetcher::kMaxConcurrentRequests = 5;
+namespace {
+constexpr int kMaxConcurrentRequests = 5;
+}
 
 LyricsFetcher::LyricsFetcher(SharedPtr<LyricsProviders> lyrics_providers, QObject *parent)
     : QObject(parent),
diff --git a/src/lyrics/lyricsfetcher.h b/src/lyrics/lyricsfetcher.h
index b214af2b..73af6956 100644
--- a/src/lyrics/lyricsfetcher.h
+++ b/src/lyrics/lyricsfetcher.h
@@ -69,8 +69,6 @@ class LyricsFetcher : public QObject {
   void StartRequests();
 
  private:
-  static const int kMaxConcurrentRequests;
-
   SharedPtr<LyricsProviders> lyrics_providers_;
   quint64 next_id_;
 
diff --git a/src/lyrics/lyricsfetchersearch.cpp b/src/lyrics/lyricsfetchersearch.cpp
index eeabf566..c5276bb1 100644
--- a/src/lyrics/lyricsfetchersearch.cpp
+++ b/src/lyrics/lyricsfetchersearch.cpp
@@ -34,9 +34,11 @@
 #include "lyricsprovider.h"
 #include "lyricsproviders.h"
 
-const int LyricsFetcherSearch::kSearchTimeoutMs = 3000;
-const int LyricsFetcherSearch::kGoodLyricsLength = 60;
-const float LyricsFetcherSearch::kHighScore = 2.5;
+namespace {
+constexpr int kSearchTimeoutMs = 3000;
+constexpr int kGoodLyricsLength = 60;
+constexpr float kHighScore = 2.5;
+}  // namespace
 
 LyricsFetcherSearch::LyricsFetcherSearch(const quint64 id, const LyricsSearchRequest &request, QObject *parent)
     : QObject(parent),
diff --git a/src/lyrics/lyricsfetchersearch.h b/src/lyrics/lyricsfetchersearch.h
index f20367e0..5af5179c 100644
--- a/src/lyrics/lyricsfetchersearch.h
+++ b/src/lyrics/lyricsfetchersearch.h
@@ -57,10 +57,6 @@ class LyricsFetcherSearch : public QObject {
   static bool LyricsSearchResultCompareScore(const LyricsSearchResult &a, const LyricsSearchResult &b);
 
  private:
-  static const int kSearchTimeoutMs;
-  static const int kGoodLyricsLength;
-  static const float kHighScore;
-
   quint64 id_;
   LyricsSearchRequest request_;
   LyricsSearchResults results_;
diff --git a/src/moodbar/moodbarpipeline.cpp b/src/moodbar/moodbarpipeline.cpp
index 664a3232..1849d9a9 100644
--- a/src/moodbar/moodbarpipeline.cpp
+++ b/src/moodbar/moodbarpipeline.cpp
@@ -41,7 +41,9 @@
 
 using std::make_unique;
 
-const int MoodbarPipeline::kBands = 128;
+namespace {
+constexpr int kBands = 128;
+}
 
 MoodbarPipeline::MoodbarPipeline(const QUrl &url, QObject *parent)
     : QObject(parent),
diff --git a/src/moodbar/moodbarpipeline.h b/src/moodbar/moodbarpipeline.h
index bedbd9d9..9c752dfe 100644
--- a/src/moodbar/moodbarpipeline.h
+++ b/src/moodbar/moodbarpipeline.h
@@ -63,8 +63,6 @@ class MoodbarPipeline : public QObject {
   static GstBusSyncReply BusCallbackSync(GstBus*, GstMessage *msg, gpointer data);
 
  private:
-  static const int kBands;
-
   QUrl url_;
   GstElement *pipeline_;
   GstElement *convert_element_;
diff --git a/src/organize/organize.cpp b/src/organize/organize.cpp
index 42b2b39d..c8696217 100644
--- a/src/organize/organize.cpp
+++ b/src/organize/organize.cpp
@@ -51,10 +51,10 @@ using namespace std::chrono_literals;
 
 class OrganizeFormat;
 
-const int Organize::kBatchSize = 10;
-#ifdef HAVE_GSTREAMER
-const int Organize::kTranscodeProgressInterval = 500;
-#endif
+namespace {
+constexpr int kBatchSize = 10;
+constexpr int kTranscodeProgressInterval = 500;
+}  // namespace
 
 Organize::Organize(SharedPtr<TaskManager> task_manager, SharedPtr<MusicStorage> destination, const OrganizeFormat &format, const bool copy, const bool overwrite, const bool albumcover, const NewSongInfoList &songs_info, const bool eject_after, const QString &playlist, QObject *parent)
     : QObject(parent),
diff --git a/src/organize/organize.h b/src/organize/organize.h
index 7868a35e..e822a7d3 100644
--- a/src/organize/organize.h
+++ b/src/organize/organize.h
@@ -66,11 +66,6 @@ class Organize : public QObject {
   explicit Organize(SharedPtr<TaskManager> task_manager, SharedPtr<MusicStorage> destination, const OrganizeFormat &format, const bool copy, const bool overwrite, const bool albumcover, const NewSongInfoList &songs, const bool eject_after, const QString &playlist = QString(), QObject *parent = nullptr);
   ~Organize() override;
 
-  static const int kBatchSize;
-#ifdef HAVE_GSTREAMER
-  static const int kTranscodeProgressInterval;
-#endif
-
   void Start();
 
  signals:
diff --git a/src/playlist/playlistbackend.cpp b/src/playlist/playlistbackend.cpp
index adba1609..5cd4be5b 100644
--- a/src/playlist/playlistbackend.cpp
+++ b/src/playlist/playlistbackend.cpp
@@ -55,7 +55,9 @@
 
 using std::make_shared;
 
-const int PlaylistBackend::kSongTableJoins = 2;
+namespace {
+constexpr int kSongTableJoins = 2;
+}
 
 PlaylistBackend::PlaylistBackend(Application *app, QObject *parent)
     : QObject(parent),
diff --git a/src/playlist/playlistbackend.h b/src/playlist/playlistbackend.h
index 82e4cc2c..ffe599d0 100644
--- a/src/playlist/playlistbackend.h
+++ b/src/playlist/playlistbackend.h
@@ -64,8 +64,6 @@ class PlaylistBackend : public QObject {
   };
   using PlaylistList = QList<Playlist>;
 
-  static const int kSongTableJoins;
-
   void Close();
   void ExitAsync();
 
diff --git a/src/playlist/playlistcontainer.cpp b/src/playlist/playlistcontainer.cpp
index 880abb8b..af1cd56a 100644
--- a/src/playlist/playlistcontainer.cpp
+++ b/src/playlist/playlistcontainer.cpp
@@ -61,9 +61,11 @@
 #include "widgets/qsearchfield.h"
 #include "settings/appearancesettingspage.h"
 
-const char *PlaylistContainer::kSettingsGroup = "Playlist";
-const int PlaylistContainer::kFilterDelayMs = 100;
-const int PlaylistContainer::kFilterDelayPlaylistSizeThreshold = 5000;
+namespace {
+constexpr char kSettingsGroup[] = "Playlist";
+constexpr int kFilterDelayMs = 100;
+constexpr int kFilterDelayPlaylistSizeThreshold = 5000;
+}  // namespace
 
 PlaylistContainer::PlaylistContainer(QWidget *parent)
     : QWidget(parent),
diff --git a/src/playlist/playlistcontainer.h b/src/playlist/playlistcontainer.h
index d993d960..8270fc6a 100644
--- a/src/playlist/playlistcontainer.h
+++ b/src/playlist/playlistcontainer.h
@@ -54,8 +54,6 @@ class PlaylistContainer : public QWidget {
   explicit PlaylistContainer(QWidget *parent = nullptr);
   ~PlaylistContainer() override;
 
-  static const char *kSettingsGroup;
-
   void SetActions(QAction *new_playlist, QAction *load_playlist, QAction *save_playlist, QAction *clear_playlist, QAction *next_playlist, QAction *previous_playlist, QAction *save_all_playlists);
   void SetManager(SharedPtr<PlaylistManager> manager);
   void ReloadSettings();
@@ -113,9 +111,6 @@ class PlaylistContainer : public QWidget {
   void RepositionNoMatchesLabel(bool force = false);
 
  private:
-  static const int kFilterDelayMs;
-  static const int kFilterDelayPlaylistSizeThreshold;
-
   Ui_PlaylistContainer *ui_;
 
   SharedPtr<PlaylistManager> manager_;
diff --git a/src/playlist/playlistdelegates.cpp b/src/playlist/playlistdelegates.cpp
index f031a400..0b1799bf 100644
--- a/src/playlist/playlistdelegates.cpp
+++ b/src/playlist/playlistdelegates.cpp
@@ -71,13 +71,15 @@
 #include "playlist/playlist.h"
 #include "playlistdelegates.h"
 
-const int QueuedItemDelegate::kQueueBoxBorder = 1;
-const int QueuedItemDelegate::kQueueBoxCornerRadius = 3;
-const int QueuedItemDelegate::kQueueBoxLength = 30;
-const QRgb QueuedItemDelegate::kQueueBoxGradientColor1 = qRgb(102, 150, 227);
-const QRgb QueuedItemDelegate::kQueueBoxGradientColor2 = qRgb(77, 121, 200);
-const int QueuedItemDelegate::kQueueOpacitySteps = 10;
-const float QueuedItemDelegate::kQueueOpacityLowerBound = 0.4F;
+namespace {
+constexpr int kQueueBoxBorder = 1;
+constexpr int kQueueBoxCornerRadius = 3;
+constexpr int kQueueBoxLength = 30;
+constexpr QRgb kQueueBoxGradientColor1 = qRgb(102, 150, 227);
+constexpr QRgb kQueueBoxGradientColor2 = qRgb(77, 121, 200);
+constexpr int kQueueOpacitySteps = 10;
+constexpr float kQueueOpacityLowerBound = 0.4F;
+}  // namespace
 
 const int PlaylistDelegateBase::kMinHeight = 19;
 
diff --git a/src/playlist/playlistdelegates.h b/src/playlist/playlistdelegates.h
index d58cb999..e60eb855 100644
--- a/src/playlist/playlistdelegates.h
+++ b/src/playlist/playlistdelegates.h
@@ -66,14 +66,6 @@ class QueuedItemDelegate : public QStyledItemDelegate {
   int queue_indicator_size(const QModelIndex &idx) const;
 
  private:
-  static const int kQueueBoxBorder;
-  static const int kQueueBoxCornerRadius;
-  static const int kQueueBoxLength;
-  static const QRgb kQueueBoxGradientColor1;
-  static const QRgb kQueueBoxGradientColor2;
-  static const int kQueueOpacitySteps;
-  static const float kQueueOpacityLowerBound;
-
   int indicator_column_;
 };
 
diff --git a/src/playlist/playlistlistview.cpp b/src/playlist/playlistlistview.cpp
index 85fb6cd7..51ec83be 100644
--- a/src/playlist/playlistlistview.cpp
+++ b/src/playlist/playlistlistview.cpp
@@ -33,6 +33,10 @@
 #include "playlistlistview.h"
 #include "playlist.h"
 
+namespace {
+constexpr int kDragHoverTimeout = 500;
+}
+
 PlaylistListView::PlaylistListView(QWidget *parent) : AutoExpandingTreeView(parent) {}
 
 void PlaylistListView::paintEvent(QPaintEvent *event) {
diff --git a/src/playlist/playlistlistview.h b/src/playlist/playlistlistview.h
index 89847f2e..29830db2 100644
--- a/src/playlist/playlistlistview.h
+++ b/src/playlist/playlistlistview.h
@@ -62,8 +62,6 @@ class PlaylistListView : public AutoExpandingTreeView {
   void timerEvent(QTimerEvent *e) override;
 
  private:
-  static const int kDragHoverTimeout = 500;
-
   QBasicTimer drag_hover_timer_;
 };
 
diff --git a/src/playlist/playlisttabbar.cpp b/src/playlist/playlisttabbar.cpp
index c3e09ee6..7684cf5f 100644
--- a/src/playlist/playlisttabbar.cpp
+++ b/src/playlist/playlisttabbar.cpp
@@ -54,7 +54,10 @@
 #include "playlistmanager.h"
 #include "playlisttabbar.h"
 
-const char *PlaylistTabBar::kSettingsGroup = "PlaylistTabBar";
+namespace {
+constexpr char kSettingsGroup[] = "PlaylistTabBar";
+constexpr int kDragHoverTimeout = 500;
+}  // namespace
 
 PlaylistTabBar::PlaylistTabBar(QWidget *parent)
     : QTabBar(parent),
diff --git a/src/playlist/playlisttabbar.h b/src/playlist/playlisttabbar.h
index 589e52e2..7657cf1b 100644
--- a/src/playlist/playlisttabbar.h
+++ b/src/playlist/playlisttabbar.h
@@ -54,9 +54,6 @@ class PlaylistTabBar : public QTabBar {
  public:
   explicit PlaylistTabBar(QWidget *parent = nullptr);
 
-  static const int kDragHoverTimeout = 500;
-  static const char *kSettingsGroup;
-
   void SetActions(QAction *new_playlist, QAction *load_playlist);
   void SetManager(SharedPtr<PlaylistManager> manager);
 
diff --git a/src/playlist/playlistview.cpp b/src/playlist/playlistview.cpp
index 7258bcfd..e8b3385e 100644
--- a/src/playlist/playlistview.cpp
+++ b/src/playlist/playlistview.cpp
@@ -81,10 +81,12 @@
 #  include "moodbar/moodbaritemdelegate.h"
 #endif
 
-const int PlaylistView::kGlowIntensitySteps = 24;
-const int PlaylistView::kAutoscrollGraceTimeout = 30;  // seconds
-const int PlaylistView::kDropIndicatorWidth = 2;
-const int PlaylistView::kDropIndicatorGradientWidth = 5;
+namespace {
+constexpr int kGlowIntensitySteps = 24;
+constexpr int kAutoscrollGraceTimeout = 30;  // seconds
+constexpr int kDropIndicatorWidth = 2;
+constexpr int kDropIndicatorGradientWidth = 5;
+}  // namespace
 
 PlaylistView::PlaylistView(QWidget *parent)
     : QTreeView(parent),
diff --git a/src/playlist/playlistview.h b/src/playlist/playlistview.h
index f28b0a82..dbed1dd2 100644
--- a/src/playlist/playlistview.h
+++ b/src/playlist/playlistview.h
@@ -186,11 +186,6 @@ class PlaylistView : public QTreeView {
   void GlowIntensityChanged();
 
  private:
-  static const int kGlowIntensitySteps;
-  static const int kAutoscrollGraceTimeout;
-  static const int kDropIndicatorWidth;
-  static const int kDropIndicatorGradientWidth;
-
   QList<int> GetEditableColumns();
   QModelIndex NextEditableIndex(const QModelIndex &current);
   QModelIndex PrevEditableIndex(const QModelIndex &current);
diff --git a/src/qobuz/qobuzservice.h b/src/qobuz/qobuzservice.h
index e9a46e90..03ddaa0a 100644
--- a/src/qobuz/qobuzservice.h
+++ b/src/qobuz/qobuzservice.h
@@ -72,7 +72,7 @@ class QobuzService : public StreamingService {
   int Search(const QString &text, StreamingSearchView::SearchType type) override;
   void CancelSearch() override;
 
-  int max_login_attempts() { return kLoginAttempts; }
+  int max_login_attempts() const { return kLoginAttempts; }
 
   Application *app() const { return app_; }
   QString app_id() const { return app_id_; }
diff --git a/src/radios/radiomodel.cpp b/src/radios/radiomodel.cpp
index c22d9441..5d657cc9 100644
--- a/src/radios/radiomodel.cpp
+++ b/src/radios/radiomodel.cpp
@@ -39,7 +39,9 @@
 #include "radiomimedata.h"
 #include "radiochannel.h"
 
-const int RadioModel::kTreeIconSize = 22;
+namespace {
+constexpr int kTreeIconSize = 22;
+}
 
 RadioModel::RadioModel(Application *app, QObject *parent)
     : SimpleTreeModel<RadioItem>(new RadioItem(this), parent),
diff --git a/src/radios/radiomodel.h b/src/radios/radiomodel.h
index 275eacd6..f5e4e886 100644
--- a/src/radios/radiomodel.h
+++ b/src/radios/radiomodel.h
@@ -86,7 +86,6 @@ class RadioModel : public SimpleTreeModel<RadioItem> {
   void AlbumCoverLoaded(const quint64 id, const AlbumCoverLoaderResult &result);
 
  private:
-  static const int kTreeIconSize;
   using ItemAndCacheKey = QPair<RadioItem*, QString>;
 
   Application *app_;
diff --git a/src/streaming/streamingsearchview.cpp b/src/streaming/streamingsearchview.cpp
index ed63bb0f..b6375537 100644
--- a/src/streaming/streamingsearchview.cpp
+++ b/src/streaming/streamingsearchview.cpp
@@ -86,9 +86,11 @@
 
 using std::make_unique;
 
-const int StreamingSearchView::kSwapModelsTimeoutMsec = 250;
-const int StreamingSearchView::kDelayedSearchTimeoutMs = 200;
-const int StreamingSearchView::kArtHeight = 32;
+namespace {
+constexpr int kSwapModelsTimeoutMsec = 250;
+constexpr int kDelayedSearchTimeoutMs = 200;
+constexpr int kArtHeight = 32;
+}  // namespace
 
 StreamingSearchView::StreamingSearchView(QWidget *parent)
     : QWidget(parent),
diff --git a/src/streaming/streamingsearchview.h b/src/streaming/streamingsearchview.h
index ee3d3fc0..363bdb72 100644
--- a/src/streaming/streamingsearchview.h
+++ b/src/streaming/streamingsearchview.h
@@ -176,11 +176,6 @@ class StreamingSearchView : public QWidget {
  public slots:
   void ReloadSettings();
 
- private:
-  static const int kSwapModelsTimeoutMsec;
-  static const int kDelayedSearchTimeoutMs;
-  static const int kArtHeight;
-
  private:
   Application *app_;
   SharedPtr<StreamingService> service_;
diff --git a/src/widgets/autoexpandingtreeview.cpp b/src/widgets/autoexpandingtreeview.cpp
index f46b9c3f..5c112e4a 100644
--- a/src/widgets/autoexpandingtreeview.cpp
+++ b/src/widgets/autoexpandingtreeview.cpp
@@ -29,7 +29,9 @@
 #include "autoexpandingtreeview.h"
 #include "core/mimedata.h"
 
-const int AutoExpandingTreeView::kRowsToShow = 50;
+namespace {
+constexpr int kRowsToShow = 50;
+}
 
 AutoExpandingTreeView::AutoExpandingTreeView(QWidget *parent)
     : QTreeView(parent),
diff --git a/src/widgets/autoexpandingtreeview.h b/src/widgets/autoexpandingtreeview.h
index 752386f9..0fb9cb51 100644
--- a/src/widgets/autoexpandingtreeview.h
+++ b/src/widgets/autoexpandingtreeview.h
@@ -39,8 +39,6 @@ class AutoExpandingTreeView : public QTreeView {
  public:
   explicit AutoExpandingTreeView(QWidget *parent = nullptr);
 
-  static const int kRowsToShow;
-
   void SetAutoOpen(bool v) { auto_open_ = v; }
   void SetExpandOnReset(bool v) { expand_on_reset_ = v; }
   void SetAddOnDoubleClick(bool v) { add_on_double_click_ = v; }
diff --git a/src/widgets/favoritewidget.cpp b/src/widgets/favoritewidget.cpp
index e421908b..a5a5a86a 100644
--- a/src/widgets/favoritewidget.cpp
+++ b/src/widgets/favoritewidget.cpp
@@ -30,7 +30,9 @@
 
 #include "favoritewidget.h"
 
-const int FavoriteWidget::kStarSize = 15;
+namespace {
+constexpr int kStarSize = 15;
+}
 
 FavoriteWidget::FavoriteWidget(const int tab_index, const bool favorite, QWidget *parent)
     : QWidget(parent),
diff --git a/src/widgets/favoritewidget.h b/src/widgets/favoritewidget.h
index 9b06f2d5..89e424f1 100644
--- a/src/widgets/favoritewidget.h
+++ b/src/widgets/favoritewidget.h
@@ -51,8 +51,6 @@ class FavoriteWidget : public QWidget {
   void mouseDoubleClickEvent(QMouseEvent*) override;
 
  private:
-  static const int kStarSize;
-
   // The playlist's id this widget belongs to
   int tab_index_;
   bool favorite_;
diff --git a/src/widgets/freespacebar.cpp b/src/widgets/freespacebar.cpp
index 772ef01d..a7f720ef 100644
--- a/src/widgets/freespacebar.cpp
+++ b/src/widgets/freespacebar.cpp
@@ -44,20 +44,23 @@
 
 class QPaintEvent;
 
-const int FreeSpaceBar::kBarHeight = 20;
-const int FreeSpaceBar::kBarBorderRadius = 8;
-const int FreeSpaceBar::kMarkerSpacing = 32;
-const int FreeSpaceBar::kLabelBoxSize = 12;
-const int FreeSpaceBar::kLabelBoxPadding = 4;
-const int FreeSpaceBar::kLabelSpacing = 16;
+namespace {
+constexpr int kBarHeight = 20;
+constexpr int kBarBorderRadius = 8;
+constexpr int kMarkerSpacing = 32;
+constexpr int kLabelBoxSize = 12;
+constexpr int kLabelBoxPadding = 4;
+constexpr int kLabelSpacing = 16;
 
-const QRgb FreeSpaceBar::kColorBg1 = qRgb(214, 207, 200);
-const QRgb FreeSpaceBar::kColorBg2 = qRgb(234, 226, 218);
-const QRgb FreeSpaceBar::kColorAdd1 = qRgb(136, 180, 229);
-const QRgb FreeSpaceBar::kColorAdd2 = qRgb(72, 146, 229);
-const QRgb FreeSpaceBar::kColorBar1 = qRgb(250, 148, 76);
-const QRgb FreeSpaceBar::kColorBar2 = qRgb(214, 102, 24);
-const QRgb FreeSpaceBar::kColorBorder = qRgb(174, 168, 162);
+constexpr QRgb kColorBg1 = qRgb(214, 207, 200);
+constexpr QRgb kColorBg2 = qRgb(234, 226, 218);
+constexpr QRgb kColorAdd1 = qRgb(136, 180, 229);
+constexpr QRgb kColorAdd2 = qRgb(72, 146, 229);
+constexpr QRgb kColorBar1 = qRgb(250, 148, 76);
+constexpr QRgb kColorBar2 = qRgb(214, 102, 24);
+constexpr QRgb kColorBorder = qRgb(174, 168, 162);
+
+}  // namespace
 
 FreeSpaceBar::FreeSpaceBar(QWidget *parent)
     : QWidget(parent),
diff --git a/src/widgets/freespacebar.h b/src/widgets/freespacebar.h
index 3a43ae00..8d85a8d2 100644
--- a/src/widgets/freespacebar.h
+++ b/src/widgets/freespacebar.h
@@ -39,21 +39,6 @@ class FreeSpaceBar : public QWidget {
  public:
   explicit FreeSpaceBar(QWidget *parent = nullptr);
 
-  static const int kBarHeight;
-  static const int kBarBorderRadius;
-  static const int kMarkerSpacing;
-  static const int kLabelBoxSize;
-  static const int kLabelBoxPadding;
-  static const int kLabelSpacing;
-
-  static const QRgb kColorBg1;
-  static const QRgb kColorBg2;
-  static const QRgb kColorAdd1;
-  static const QRgb kColorAdd2;
-  static const QRgb kColorBar1;
-  static const QRgb kColorBar2;
-  static const QRgb kColorBorder;
-
   void set_free_bytes(const quint64 bytes) { free_ = bytes; update(); }
   void set_additional_bytes(const quint64 bytes) { additional_ = bytes; update(); }
   void set_total_bytes(const quint64 bytes) { total_ = bytes; update(); }
diff --git a/src/widgets/groupediconview.cpp b/src/widgets/groupediconview.cpp
index ffbb769f..71911a7b 100644
--- a/src/widgets/groupediconview.cpp
+++ b/src/widgets/groupediconview.cpp
@@ -47,8 +47,10 @@
 #include "core/multisortfilterproxy.h"
 #include "groupediconview.h"
 
-const int GroupedIconView::kBarThickness = 2;
-const int GroupedIconView::kBarMarginTop = 3;
+namespace {
+constexpr int kBarThickness = 2;
+constexpr int kBarMarginTop = 3;
+}  // namespace
 
 GroupedIconView::GroupedIconView(QWidget *parent)
     : QListView(parent),
diff --git a/src/widgets/groupediconview.h b/src/widgets/groupediconview.h
index 20aa0343..6d097d1c 100644
--- a/src/widgets/groupediconview.h
+++ b/src/widgets/groupediconview.h
@@ -100,9 +100,6 @@ class GroupedIconView : public QListView {
   void LayoutItems();
 
  private:
-  static const int kBarThickness;
-  static const int kBarMarginTop;
-
   struct Header {
     int y;
     int first_row;
diff --git a/src/widgets/multiloadingindicator.cpp b/src/widgets/multiloadingindicator.cpp
index 6986714c..a7c99850 100644
--- a/src/widgets/multiloadingindicator.cpp
+++ b/src/widgets/multiloadingindicator.cpp
@@ -34,9 +34,11 @@
 #include "multiloadingindicator.h"
 #include "widgets/busyindicator.h"
 
-const int MultiLoadingIndicator::kVerticalPadding = 4;
-const int MultiLoadingIndicator::kHorizontalPadding = 6;
-const int MultiLoadingIndicator::kSpacing = 6;
+namespace {
+constexpr int kVerticalPadding = 4;
+constexpr int kHorizontalPadding = 6;
+constexpr int kSpacing = 6;
+}
 
 MultiLoadingIndicator::MultiLoadingIndicator(QWidget *parent)
     : QWidget(parent),
diff --git a/src/widgets/multiloadingindicator.h b/src/widgets/multiloadingindicator.h
index 9cc06d0f..a2f6e2fa 100644
--- a/src/widgets/multiloadingindicator.h
+++ b/src/widgets/multiloadingindicator.h
@@ -39,10 +39,6 @@ class MultiLoadingIndicator : public QWidget {
  public:
   explicit MultiLoadingIndicator(QWidget *parent = nullptr);
 
-  static const int kVerticalPadding;
-  static const int kHorizontalPadding;
-  static const int kSpacing;
-
   void SetTaskManager(SharedPtr<TaskManager> task_manager);
 
   QSize sizeHint() const override;
diff --git a/src/widgets/playingwidget.cpp b/src/widgets/playingwidget.cpp
index 70c2f31b..01d96645 100644
--- a/src/widgets/playingwidget.cpp
+++ b/src/widgets/playingwidget.cpp
@@ -47,21 +47,25 @@
 
 using std::make_unique;
 
-const char *PlayingWidget::kSettingsGroup = "PlayingWidget";
+namespace {
+
+constexpr char kSettingsGroup[] = "PlayingWidget";
 
 // Space between the cover and the details in small mode
-const int PlayingWidget::kPadding = 2;
+constexpr int kPadding = 2;
 
 // Width of the transparent to black gradient above and below the text in large mode
-const int PlayingWidget::kGradientHead = 40;
-const int PlayingWidget::kGradientTail = 20;
+constexpr int kGradientHead = 40;
+constexpr int kGradientTail = 20;
 
 // Maximum height of the cover in large mode, and offset between the bottom of the cover and bottom of the widget
-const int PlayingWidget::kMaxCoverSize = 260;
-const int PlayingWidget::kBottomOffset = 0;
+constexpr int kMaxCoverSize = 260;
+constexpr int kBottomOffset = 0;
 
 // Border for large mode
-const int PlayingWidget::kTopBorder = 4;
+constexpr int kTopBorder = 4;
+
+}  // namespace
 
 PlayingWidget::PlayingWidget(QWidget *parent)
     : QWidget(parent),
diff --git a/src/widgets/playingwidget.h b/src/widgets/playingwidget.h
index 82079121..8ae27e88 100644
--- a/src/widgets/playingwidget.h
+++ b/src/widgets/playingwidget.h
@@ -102,14 +102,6 @@ class PlayingWidget : public QWidget {
   void FadePreviousTrack(const qreal value);
 
  private:
-  static const char *kSettingsGroup;
-  static const int kPadding;
-  static const int kGradientHead;
-  static const int kGradientTail;
-  static const int kMaxCoverSize;
-  static const int kBottomOffset;
-  static const int kTopBorder;
-
   Application *app_;
   AlbumCoverChoiceController *album_cover_choice_controller_;
   Mode mode_;
diff --git a/src/widgets/trackslider.cpp b/src/widgets/trackslider.cpp
index e03ec637..5ffc3391 100644
--- a/src/widgets/trackslider.cpp
+++ b/src/widgets/trackslider.cpp
@@ -41,7 +41,9 @@
 #  include "moodbar/moodbarproxystyle.h"
 #endif
 
-const char *TrackSlider::kSettingsGroup = "MainWindow";
+namespace {
+constexpr char kSettingsGroup[] = "MainWindow";
+}
 
 TrackSlider::TrackSlider(QWidget *parent)
     : QWidget(parent),
diff --git a/src/widgets/trackslider.h b/src/widgets/trackslider.h
index a435d564..562ac913 100644
--- a/src/widgets/trackslider.h
+++ b/src/widgets/trackslider.h
@@ -56,8 +56,6 @@ class TrackSlider : public QWidget {
   MoodbarProxyStyle *moodbar_style() const { return moodbar_style_; }
 #endif
 
-  static const char *kSettingsGroup;
-
  public slots:
   void SetValue(const int elapsed, const int total);
   void SetStopped();
diff --git a/src/widgets/tracksliderpopup.cpp b/src/widgets/tracksliderpopup.cpp
index 063f8225..4b5c5141 100644
--- a/src/widgets/tracksliderpopup.cpp
+++ b/src/widgets/tracksliderpopup.cpp
@@ -36,11 +36,13 @@
 #include "core/qt_blurimage.h"
 #include "tracksliderpopup.h"
 
-const int TrackSliderPopup::kTextMargin = 4;
-const int TrackSliderPopup::kPointLength = 16;
-const int TrackSliderPopup::kPointWidth = 4;
-const int TrackSliderPopup::kBorderRadius = 4;
-const qreal TrackSliderPopup::kBlurRadius = 20.0;
+namespace {
+constexpr int kTextMargin = 4;
+constexpr int kPointLength = 16;
+constexpr int kPointWidth = 4;
+constexpr int kBorderRadius = 4;
+constexpr qreal kBlurRadius = 20.0;
+}  // namespace
 
 TrackSliderPopup::TrackSliderPopup(QWidget *parent)
     : QWidget(parent),
diff --git a/src/widgets/tracksliderpopup.h b/src/widgets/tracksliderpopup.h
index 3cdbc6ed..e458880e 100644
--- a/src/widgets/tracksliderpopup.h
+++ b/src/widgets/tracksliderpopup.h
@@ -48,12 +48,6 @@ class TrackSliderPopup : public QWidget {
   void paintEvent(QPaintEvent*) override;
 
  private:
-  static const int kTextMargin;
-  static const int kPointLength;
-  static const int kPointWidth;
-  static const int kBorderRadius;
-  static const qreal kBlurRadius;
-
   void UpdatePixmap();
   void UpdatePosition();
   void SendMouseEventToParent(QMouseEvent *e);