diff --git a/widget/PuppetWidget.cpp b/widget/PuppetWidget.cpp
index 6bc1b794e13b..2891b469fb90 100644
--- a/widget/PuppetWidget.cpp
+++ b/widget/PuppetWidget.cpp
@@ -1156,15 +1156,6 @@ LayoutDeviceIntRect PuppetWidget::GetScreenBounds() {
   return LayoutDeviceIntRect(WidgetToScreenOffset(), mBounds.Size());
 }
 
-LayoutDeviceIntSize PuppetWidget::GetCompositionSize() {
-  Maybe<LayoutDeviceIntRect> visibleRect =
-      mBrowserChild ? mBrowserChild->GetVisibleRect() : Nothing();
-  if (!visibleRect) {
-    return nsBaseWidget::GetCompositionSize();
-  }
-  return visibleRect->Size();
-}
-
 uint32_t PuppetWidget::GetMaxTouchPoints() const {
   return mBrowserChild ? mBrowserChild->MaxTouchPoints() : 0;
 }
diff --git a/widget/PuppetWidget.h b/widget/PuppetWidget.h
index 6c6dcfb3d897..00a8a0969313 100644
--- a/widget/PuppetWidget.h
+++ b/widget/PuppetWidget.h
@@ -248,8 +248,6 @@ class PuppetWidget : public nsBaseWidget,
 
   virtual LayoutDeviceIntRect GetScreenBounds() override;
 
-  virtual LayoutDeviceIntSize GetCompositionSize() override;
-
   [[nodiscard]] virtual nsresult StartPluginIME(
       const mozilla::WidgetKeyboardEvent& aKeyboardEvent, int32_t aPanelX,
       int32_t aPanelY, nsString& aCommitted) override;
diff --git a/widget/nsIWidget.h b/widget/nsIWidget.h
index 035093be17aa..c98a25072744 100644
--- a/widget/nsIWidget.h
+++ b/widget/nsIWidget.h
@@ -939,16 +939,6 @@ class nsIWidget : public nsISupports {
     return GetClientBounds().Size();
   }
 
-  /**
-   * Get the size of the bounds of this widget that will be visible when
-   * rendered.
-   *
-   * @return the width and height of the composition size of this widget.
-   */
-  virtual LayoutDeviceIntSize GetCompositionSize() {
-    return GetBounds().Size();
-  }
-
   /**
    * Set the background color for this widget
    *