Fixes issues 3883 and 5194
diff --git a/Lib/idlelib/MultiCall.py b/Lib/idlelib/MultiCall.py
index 51de639..b228f57 100644
--- a/Lib/idlelib/MultiCall.py
+++ b/Lib/idlelib/MultiCall.py
@@ -33,6 +33,7 @@
 import string
 import re
 import Tkinter
+import macosxSupport
 
 # the event type constants, which define the meaning of mc_type
 MC_KEYPRESS=0; MC_KEYRELEASE=1; MC_BUTTONPRESS=2; MC_BUTTONRELEASE=3;
@@ -45,7 +46,7 @@
 MC_OPTION = 1<<6; MC_COMMAND = 1<<7
 
 # define the list of modifiers, to be used in complex event types.
-if sys.platform == "darwin" and sys.executable.count(".app"):
+if macosxSupport.runningAsOSXApp():
     _modifiers = (("Shift",), ("Control",), ("Option",), ("Command",))
     _modifier_masks = (MC_SHIFT, MC_CONTROL, MC_OPTION, MC_COMMAND)
 else: