diff --git a/Lib/idlelib/NEWS.txt b/Lib/idlelib/NEWS.txt
index 46ef3cb..205b9f3 100644
--- a/Lib/idlelib/NEWS.txt
+++ b/Lib/idlelib/NEWS.txt
@@ -1,3 +1,10 @@
+What's New in IDLE 2.7.3?
+=======================
+
+- Issue #3573: IDLE hangs when passing invalid command line args
+  (directory(ies) instead of file(s)).
+
+
 What's New in IDLE 2.7.2?
 =======================
 
diff --git a/Lib/idlelib/PyShell.py b/Lib/idlelib/PyShell.py
index 895d7da..eeb33e1 100644
--- a/Lib/idlelib/PyShell.py
+++ b/Lib/idlelib/PyShell.py
@@ -1412,8 +1412,10 @@
 
     if enable_edit:
         if not (cmd or script):
-            for filename in args:
-                flist.open(filename)
+            for filename in args[:]:
+                if flist.open(filename) is None:
+                    # filename is a directory actually, disconsider it
+                    args.remove(filename)
             if not args:
                 flist.new()
     if enable_shell: