diff --git a/redo/area_darwin.go b/redo/area_darwin.go
index b6140b2..1cb2e4b 100644
--- a/redo/area_darwin.go
+++ b/redo/area_darwin.go
@@ -60,25 +60,17 @@ func areaView_drawRect(self C.id, rect C.struct_xrect, data unsafe.Pointer) {
 }
 
 func parseModifiers(e C.id) (m Modifiers) {
-	const (
-		// TODO define these on the Objective-C side
-		_NSShiftKeyMask     = 1 << 17
-		_NSControlKeyMask   = 1 << 18
-		_NSAlternateKeyMask = 1 << 19
-		_NSCommandKeyMask   = 1 << 20
-	)
-
-	mods := uintptr(C.modifierFlags(e))
-	if (mods & _NSControlKeyMask) != 0 {
+	mods := C.modifierFlags(e)
+	if (mods & C.cNSControlKeyMask) != 0 {
 		m |= Ctrl
 	}
-	if (mods & _NSAlternateKeyMask) != 0 {
+	if (mods & C.cNSAlternateKeyMask) != 0 {
 		m |= Alt
 	}
-	if (mods & _NSShiftKeyMask) != 0 {
+	if (mods & C.cNSShiftKeyMask) != 0 {
 		m |= Shift
 	}
-	if (mods & _NSCommandKeyMask) != 0 {
+	if (mods & C.cNSCommandKeyMask) != 0 {
 		m |= Super
 	}
 	return m
diff --git a/redo/area_darwin.m b/redo/area_darwin.m
index 1f7ece6..f99737f 100644
--- a/redo/area_darwin.m
+++ b/redo/area_darwin.m
@@ -140,6 +140,12 @@ BOOL drawImage(void *pixels, intptr_t width, intptr_t height, intptr_t stride, i
 	return success;
 }
 
+// can't include the header file with these from the Go side since it's an Objective-C header file; keep them here to be safe
+const uintptr_t cNSShiftKeyMask = (uintptr_t) NSShiftKeyMask;
+const uintptr_t cNSControlKeyMask = (uintptr_t) NSControlKeyMask;
+const uintptr_t cNSAlternateKeyMask = (uintptr_t) NSAlternateKeyMask;
+const uintptr_t cNSCommandKeyMask = (uintptr_t) NSCommandKeyMask;
+
 uintptr_t modifierFlags(id e)
 {
 	return fromNSUInteger([toNSEvent(e) modifierFlags]);
diff --git a/redo/objc_darwin.h b/redo/objc_darwin.h
index 99089fc..dd5ff9d 100644
--- a/redo/objc_darwin.h
+++ b/redo/objc_darwin.h
@@ -102,6 +102,10 @@ extern struct xalignment alignmentInfoFrame(id);
 extern Class getAreaClass(void);
 extern id newArea(void *);
 extern BOOL drawImage(void *, intptr_t, intptr_t, intptr_t, intptr_t, intptr_t);
+extern const uintptr_t cNSShiftKeyMask;
+extern const uintptr_t cNSControlKeyMask;
+extern const uintptr_t cNSAlternateKeyMask;
+extern const uintptr_t cNSCommandKeyMask;
 extern uintptr_t modifierFlags(id);
 extern struct xpoint getTranslatedEventPoint(id, id);
 extern intptr_t buttonNumber(id);