diff --git chrome/browser/printing/printer_query.cc chrome/browser/printing/printer_query.cc
index 5786a450fdb6..2abaa6e3168e 100644
--- chrome/browser/printing/printer_query.cc
+++ chrome/browser/printing/printer_query.cc
@@ -12,6 +12,7 @@
 #include "base/location.h"
 #include "base/task/post_task.h"
 #include "base/threading/thread_restrictions.h"
+#include "base/threading/thread_task_runner_handle.h"
 #include "base/values.h"
 #include "chrome/browser/printing/print_job_worker.h"
 #include "content/public/browser/browser_task_traits.h"
@@ -22,7 +23,9 @@
 namespace printing {
 
 PrinterQuery::PrinterQuery(int render_process_id, int render_frame_id)
-    : cookie_(PrintSettings::NewCookie()),
+    : base::RefCountedDeleteOnSequence<PrinterQuery>(
+          base::ThreadTaskRunnerHandle::Get()),
+      cookie_(PrintSettings::NewCookie()),
       worker_(std::make_unique<PrintJobWorker>(render_process_id,
                                                render_frame_id,
                                                this)) {
@@ -57,7 +60,7 @@ void PrinterQuery::GetSettingsDone(const PrintSettings& new_settings,
 }
 
 std::unique_ptr<PrintJobWorker> PrinterQuery::DetachWorker() {
-  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   DCHECK(!callback_);
   DCHECK(worker_);
 
diff --git chrome/browser/printing/printer_query.h chrome/browser/printing/printer_query.h
index 6d9b0e74196f..b6d8e2220d02 100644
--- chrome/browser/printing/printer_query.h
+++ chrome/browser/printing/printer_query.h
@@ -9,7 +9,7 @@
 
 #include "base/callback.h"
 #include "base/macros.h"
-#include "base/memory/ref_counted.h"
+#include "base/memory/ref_counted_delete_on_sequence.h"
 #include "base/values.h"
 #include "printing/print_job_constants.h"
 #include "printing/print_settings.h"
@@ -24,7 +24,7 @@ namespace printing {
 class PrintJobWorker;
 
 // Query the printer for settings.
-class PrinterQuery : public base::RefCountedThreadSafe<PrinterQuery> {
+class PrinterQuery : public base::RefCountedDeleteOnSequence<PrinterQuery> {
  public:
   // GetSettings() UI parameter.
   enum class GetSettingsAskParam {
@@ -41,6 +41,8 @@ class PrinterQuery : public base::RefCountedThreadSafe<PrinterQuery> {
 
   // Detach the PrintJobWorker associated to this object. Virtual so that tests
   // can override.
+  // Called on the UI thread.
+  // TODO(thestig): Do |worker_| and |callback_| need locks?
   virtual std::unique_ptr<PrintJobWorker> DetachWorker();
 
   // Virtual so that tests can override.
@@ -84,8 +86,9 @@ class PrinterQuery : public base::RefCountedThreadSafe<PrinterQuery> {
   bool PostTask(const base::Location& from_here, base::OnceClosure task);
 
  protected:
-  // Refcounted class.
-  friend class base::RefCountedThreadSafe<PrinterQuery>;
+  // RefCountedDeleteOnSequence class.
+  friend class base::RefCountedDeleteOnSequence<PrinterQuery>;
+  friend class base::DeleteHelper<PrinterQuery>;
 
   virtual ~PrinterQuery();