diff --git a/src/core/mac_startup.mm b/src/core/mac_startup.mm
index 003a34a7f..d1b42595e 100644
--- a/src/core/mac_startup.mm
+++ b/src/core/mac_startup.mm
@@ -19,6 +19,7 @@
  */
 
 #import <AppKit/NSApplication.h>
+#import <AppKit/NSWindow.h>
 #import <AppKit/NSEvent.h>
 #import <AppKit/NSGraphics.h>
 #import <AppKit/NSNibDeclarations.h>