--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -4300,17 +4300,16 @@ nsWindow::SetTransparencyMode(nsTranspar
         if (!topWindow)
             return;
 
         topWindow->SetTransparencyMode(aMode);
         return;
     }
 
     if (mWindowType != eWindowType_popup) {
-        NS_WARNING("Cannot set transparency mode on non-popup windows.");
         return;
     }
 
     bool isTransparent = aMode == eTransparencyTransparent;
 
     if (mIsTransparent == isTransparent)
         return;