diff --git a/src/posix/cocoa/i_common.h b/src/posix/cocoa/i_common.h
index 63377bb36..cf2fffbdc 100644
--- a/src/posix/cocoa/i_common.h
+++ b/src/posix/cocoa/i_common.h
@@ -62,6 +62,11 @@ extern RenderBufferOptions rbOpts;
 #define AppKit10_7 1138
 
 
+@interface NSWindow(ExitAppOnClose)
+- (void)exitAppOnClose;
+@end
+
+
 inline bool I_IsHiDPISupported()
 {
 	return NSAppKitVersionNumber >= AppKit10_7;
diff --git a/src/posix/cocoa/i_video.mm b/src/posix/cocoa/i_video.mm
index a47a1f1a8..768d147a9 100644
--- a/src/posix/cocoa/i_video.mm
+++ b/src/posix/cocoa/i_video.mm
@@ -58,6 +58,18 @@
 #undef Class
 
 
+@implementation NSWindow(ExitAppOnClose)
+
+- (void)exitAppOnClose
+{
+	NSButton* closeButton = [self standardWindowButton:NSWindowCloseButton];
+	[closeButton setAction:@selector(terminate:)];
+	[closeButton setTarget:NSApp];
+}
+
+@end
+
+
 EXTERN_CVAR(Bool, ticker   )
 EXTERN_CVAR(Bool, vid_vsync)
 EXTERN_CVAR(Bool, vid_hidpi)
@@ -659,10 +671,7 @@ void CocoaVideo::SetWindowedMode(const int width, const int height)
 
 	[m_window setContentSize:windowSize];
 	[m_window center];
-
-	NSButton* closeButton = [m_window standardWindowButton:NSWindowCloseButton];
-	[closeButton setAction:@selector(terminate:)];
-	[closeButton setTarget:NSApp];
+	[m_window exitAppOnClose];
 }
 
 void CocoaVideo::SetMode(const int width, const int height, const bool fullscreen, const bool hiDPI)