--- a/widget/cocoa/nsCocoaWindow.mm
+++ b/widget/cocoa/nsCocoaWindow.mm
@@ -3320,17 +3320,17 @@ static const NSString* kStateShowsToolba
   if (!NSEqualRects(mWindowButtonsRect, aRect)) {
     mWindowButtonsRect = aRect;
     [self reflowTitlebarElements];
   }
 }
 
 - (NSPoint)windowButtonsPositionWithDefaultPosition:(NSPoint)aDefaultPosition
 {
-  if ([self drawsContentsIntoWindowFrame]) {
+  if ([self drawsContentsIntoWindowFrame] && !([self styleMask] & NSFullScreenWindowMask)) {
     if (NSIsEmptyRect(mWindowButtonsRect)) {
       // Empty rect. Let's hide the buttons.
       // Position is in non-flipped window coordinates. Using frame's height
       // for the vertical coordinate will move the buttons above the window,
       // making them invisible.
       return NSMakePoint(0, [self frame].size.height);
     }
     return NSMakePoint(mWindowButtonsRect.origin.x, mWindowButtonsRect.origin.y);