diff --git a/src/Fl_cocoa.mm b/src/Fl_cocoa.mm
index 725d2c201..6a21dac78 100644
--- a/src/Fl_cocoa.mm
+++ b/src/Fl_cocoa.mm
@@ -165,6 +165,7 @@ const NSUInteger NSEventModifierFlagOption = NSAlternateKeyMask;
 const NSUInteger NSEventModifierFlagControl = NSControlKeyMask;
 const NSUInteger NSEventModifierFlagShift = NSShiftKeyMask;
 const NSUInteger NSEventModifierFlagCapsLock = NSAlphaShiftKeyMask;
+const NSUInteger NSEventModifierFlagFunction = NSFunctionKeyMask;
 
 const NSEventType NSEventTypeLeftMouseDown = NSLeftMouseDown;
 const NSEventType NSEventTypeRightMouseDown = NSRightMouseDown;