diff --git a/gdk/quartz/GdkQuartzNSWindow.c b/gdk/quartz/GdkQuartzNSWindow.c
index 92fb8079bd..8d1ba4af2b 100644
--- a/gdk/quartz/GdkQuartzNSWindow.c
+++ b/gdk/quartz/GdkQuartzNSWindow.c
@@ -278,7 +278,7 @@
                              screen:screen];
 
   [self setAcceptsMouseMovedEvents:YES];
-  [self setDelegate:self];
+  [self setDelegate:(id<NSWindowDelegate>)self];
   [self setReleasedWhenClosed:YES];
 
   return self;