diff --git a/3rdparty/kdsingleapplication/kdsingleapplication.cpp b/3rdparty/kdsingleapplication/kdsingleapplication.cpp
index f80553833..0fbdb1d99 100644
--- a/3rdparty/kdsingleapplication/kdsingleapplication.cpp
+++ b/3rdparty/kdsingleapplication/kdsingleapplication.cpp
@@ -23,8 +23,6 @@ class KDSingleApplicationPrivate
 public:
     explicit KDSingleApplicationPrivate(const QString &name, KDSingleApplication *q);
 
-    void initialize();
-
     QString name() const
     {
         return m_name;