diff --git a/gfx/tests/gtest/TestCompositor.cpp b/gfx/tests/gtest/TestCompositor.cpp
index 53286602e6d2..05e9fbe40634 100644
--- a/gfx/tests/gtest/TestCompositor.cpp
+++ b/gfx/tests/gtest/TestCompositor.cpp
@@ -78,7 +78,7 @@ public:
   virtual nsresult        SetFocus(bool aRaise) override { return NS_OK; }
   virtual nsresult        ConfigureChildren(const nsTArray<Configuration>& aConfigurations) override { return NS_OK; }
   virtual void            Invalidate(const LayoutDeviceIntRect& aRect) override {}
-  NS_IMETHOD              SetTitle(const nsAString& title) override { return NS_OK; }
+  virtual nsresult        SetTitle(const nsAString& title) override { return NS_OK; }
   virtual LayoutDeviceIntPoint WidgetToScreenOffset() override { return LayoutDeviceIntPoint(0, 0); }
   NS_IMETHOD              DispatchEvent(mozilla::WidgetGUIEvent* aEvent,
                                         nsEventStatus& aStatus) override { return NS_OK; }
diff --git a/widget/PuppetWidget.h b/widget/PuppetWidget.h
index 2304ff653f90..ad9f478bb34e 100644
--- a/widget/PuppetWidget.h
+++ b/widget/PuppetWidget.h
@@ -128,7 +128,7 @@ public:
 #endif
 
   // PuppetWidgets don't have any concept of titles.
-  NS_IMETHOD SetTitle(const nsAString& aTitle) override
+  virtual nsresult SetTitle(const nsAString& aTitle) override
   { return NS_ERROR_UNEXPECTED; }
 
   virtual LayoutDeviceIntPoint WidgetToScreenOffset() override
diff --git a/widget/android/nsWindow.h b/widget/android/nsWindow.h
index 34842e6b3a2b..47e652bbbc04 100644
--- a/widget/android/nsWindow.h
+++ b/widget/android/nsWindow.h
@@ -200,7 +200,7 @@ public:
     NS_IMETHOD GetHasTransparentBackground(bool& aTransparent) { aTransparent = false; return NS_OK; }
     void* GetNativeData(uint32_t aDataType) override;
     void SetNativeData(uint32_t aDataType, uintptr_t aVal) override;
-    NS_IMETHOD SetTitle(const nsAString& aTitle) override { return NS_OK; }
+    virtual nsresult SetTitle(const nsAString& aTitle) override { return NS_OK; }
     virtual MOZ_MUST_USE nsresult GetAttention(int32_t aCycleCount) override { return NS_ERROR_NOT_IMPLEMENTED; }
 
     NS_IMETHOD_(void) SetInputContext(const InputContext& aContext,
diff --git a/widget/cocoa/nsChildView.h b/widget/cocoa/nsChildView.h
index c4b6ba4da94b..ea1f73d042d9 100644
--- a/widget/cocoa/nsChildView.h
+++ b/widget/cocoa/nsChildView.h
@@ -366,7 +366,7 @@ public:
   virtual nsresult  SetCursor(imgIContainer* aCursor,
                               uint32_t aHotspotX, uint32_t aHotspotY) override;
 
-  NS_IMETHOD        SetTitle(const nsAString& title) override;
+  virtual nsresult  SetTitle(const nsAString& title) override;
 
   virtual MOZ_MUST_USE nsresult
                     GetAttention(int32_t aCycleCount) override;
diff --git a/widget/cocoa/nsChildView.mm b/widget/cocoa/nsChildView.mm
index 405de13b8b10..78d4ebb8341b 100644
--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -1610,7 +1610,8 @@ LayoutDeviceIntPoint nsChildView::WidgetToScreenOffset()
   NS_OBJC_END_TRY_ABORT_BLOCK_RETURN(LayoutDeviceIntPoint(0,0));
 }
 
-NS_IMETHODIMP nsChildView::SetTitle(const nsAString& title)
+nsresult
+nsChildView::SetTitle(const nsAString& title)
 {
   // child views don't have titles
   return NS_OK;
diff --git a/widget/cocoa/nsCocoaWindow.h b/widget/cocoa/nsCocoaWindow.h
index 1bac96459b27..9debc2262e1b 100644
--- a/widget/cocoa/nsCocoaWindow.h
+++ b/widget/cocoa/nsCocoaWindow.h
@@ -299,7 +299,7 @@ public:
       return mozilla::DesktopToLayoutDeviceScale(BackingScaleFactor());
     }
 
-    NS_IMETHOD              SetTitle(const nsAString& aTitle) override;
+    virtual nsresult        SetTitle(const nsAString& aTitle) override;
 
     virtual void Invalidate(const LayoutDeviceIntRect& aRect) override;
     virtual nsresult ConfigureChildren(const nsTArray<Configuration>& aConfigurations) override;
diff --git a/widget/cocoa/nsCocoaWindow.mm b/widget/cocoa/nsCocoaWindow.mm
index 91a10a76296f..9ea63e68946a 100644
--- a/widget/cocoa/nsCocoaWindow.mm
+++ b/widget/cocoa/nsCocoaWindow.mm
@@ -1797,7 +1797,8 @@ nsCocoaWindow::SetCursor(imgIContainer* aCursor,
   return NS_OK;
 }
 
-NS_IMETHODIMP nsCocoaWindow::SetTitle(const nsAString& aTitle)
+nsresult
+nsCocoaWindow::SetTitle(const nsAString& aTitle)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NSRESULT;
 
diff --git a/widget/gonk/nsWindow.h b/widget/gonk/nsWindow.h
index d7624b179687..a61b4c6fedb5 100644
--- a/widget/gonk/nsWindow.h
+++ b/widget/gonk/nsWindow.h
@@ -73,7 +73,7 @@ public:
     virtual void Invalidate(const LayoutDeviceIntRect& aRect);
     virtual void* GetNativeData(uint32_t aDataType);
     virtual void SetNativeData(uint32_t aDataType, uintptr_t aVal);
-    NS_IMETHOD SetTitle(const nsAString& aTitle)
+    virtual nsresult SetTitle(const nsAString& aTitle)
     {
         return NS_OK;
     }
diff --git a/widget/gtk/nsWindow.cpp b/widget/gtk/nsWindow.cpp
index 3e765fbde473..baa93704c5c9 100644
--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -1772,7 +1772,7 @@ nsWindow::SetNativeData(uint32_t aDataType, uintptr_t aVal)
     mPluginNativeWindow = (nsPluginNativeWindowGtk*)aVal;
 }
 
-NS_IMETHODIMP
+nsresult
 nsWindow::SetTitle(const nsAString& aTitle)
 {
     if (!mShell)
diff --git a/widget/gtk/nsWindow.h b/widget/gtk/nsWindow.h
index f898a44f23bc..f975593dd945 100644
--- a/widget/gtk/nsWindow.h
+++ b/widget/gtk/nsWindow.h
@@ -141,7 +141,7 @@ public:
     virtual void       Invalidate(const LayoutDeviceIntRect& aRect) override;
     virtual void*      GetNativeData(uint32_t aDataType) override;
     void               SetNativeData(uint32_t aDataType, uintptr_t aVal) override;
-    NS_IMETHOD         SetTitle(const nsAString& aTitle) override;
+    virtual nsresult   SetTitle(const nsAString& aTitle) override;
     virtual void       SetIcon(const nsAString& aIconSpec) override;
     virtual void       SetWindowClass(const nsAString& xulWinType) override;
     virtual LayoutDeviceIntPoint WidgetToScreenOffset() override;
diff --git a/widget/nsIWidget.h b/widget/nsIWidget.h
index 7e3792e9b423..e00d37e81e2a 100644
--- a/widget/nsIWidget.h
+++ b/widget/nsIWidget.h
@@ -1311,7 +1311,7 @@ class nsIWidget : public nsISupports
      *
      * @param aTitle string displayed as the title of the widget
      */
-    NS_IMETHOD SetTitle(const nsAString& aTitle) = 0;
+    virtual nsresult SetTitle(const nsAString& aTitle) = 0;
 
     /**
      * Set the widget's icon.
diff --git a/widget/uikit/nsWindow.h b/widget/uikit/nsWindow.h
index bff8f79c8dab..e9dcc88f822c 100644
--- a/widget/uikit/nsWindow.h
+++ b/widget/uikit/nsWindow.h
@@ -70,7 +70,7 @@ public:
     }
     virtual int32_t         RoundsWidgetCoordinatesTo() override;
 
-    NS_IMETHOD              SetTitle(const nsAString& aTitle) override {
+    virtual nsresult        SetTitle(const nsAString& aTitle) override {
         return NS_OK;
     }
 
diff --git a/widget/windows/nsWindow.cpp b/widget/windows/nsWindow.cpp
index 27aefcbc1d7b..8e229496a975 100644
--- a/widget/windows/nsWindow.cpp
+++ b/widget/windows/nsWindow.cpp
@@ -3529,7 +3529,8 @@ void nsWindow::FreeNativeData(void * data, uint32_t aDataType)
  *
  **************************************************************/
 
-NS_IMETHODIMP nsWindow::SetTitle(const nsAString& aTitle)
+nsresult
+nsWindow::SetTitle(const nsAString& aTitle)
 {
   const nsString& strTitle = PromiseFlatString(aTitle);
   AutoRestore<bool> sendingText(mSendingSetText);
diff --git a/widget/windows/nsWindow.h b/widget/windows/nsWindow.h
index 4a54c41838db..3c91fbe993b2 100644
--- a/widget/windows/nsWindow.h
+++ b/widget/windows/nsWindow.h
@@ -161,7 +161,7 @@ public:
   virtual void*           GetNativeData(uint32_t aDataType) override;
   void                    SetNativeData(uint32_t aDataType, uintptr_t aVal) override;
   virtual void            FreeNativeData(void * data, uint32_t aDataType) override;
-  NS_IMETHOD              SetTitle(const nsAString& aTitle) override;
+  virtual nsresult        SetTitle(const nsAString& aTitle) override;
   virtual void            SetIcon(const nsAString& aIconSpec) override;
   virtual LayoutDeviceIntPoint WidgetToScreenOffset() override;
   virtual LayoutDeviceIntSize ClientToWindowSize(const LayoutDeviceIntSize& aClientSize) override;