--- a/XWorkstation.st	Fri Feb 10 21:33:03 2017 +0100
+++ b/XWorkstation.st	Fri Feb 10 21:33:14 2017 +0100
@@ -9847,6 +9847,30 @@
     altModifierMask := aSmallInteger
 !
 
+appleAltModifierMask
+    "return the Xlib mask bit for the ALT modifier key on OS-X.
+     Nil returned for other displays"
+
+    OperatingSystem isOSXlike ifTrue:[
+        ^ 8192
+    ].
+    ^ nil
+
+    "Created: / 10-02-2017 / 21:32:13 / cg"
+!
+
+appleCmdModifierMask
+    "return the Xlib mask bit for the CMD modifier key on OS-X.
+     Nil returned for other displays"
+
+    OperatingSystem isOSXlike ifTrue:[
+        ^ 16
+    ].
+    ^ nil
+
+    "Created: / 10-02-2017 / 21:32:50 / cg"
+!
+
 ctrlModifierMask
     "return the Xlib mask bit for the control modifier key"