diff --git a/Boxer/DOS window/BXDOSWindowController.m b/Boxer/DOS window/BXDOSWindowController.m
index 11c984e9..d2765b62 100644
--- a/Boxer/DOS window/BXDOSWindowController.m	
+++ b/Boxer/DOS window/BXDOSWindowController.m	
@@ -582,7 +582,7 @@ - (IBAction) decrementFullscreenSize: (id)sender
 
 + (NSSet *) keyPathsForValuesAffectingMinFullscreenViewportSize
 {
-    return [NSSet setWithObject: @"renderingView.currentFrame.scaledResolution"];
+    return [NSSet setWithObject: @"renderingView.currentFrame"];
 }
 
 - (NSSize) minFullscreenViewportSize