Index: source/blender/python/api2_2x/Window.c
===================================================================
--- source/blender/python/api2_2x/Window.c (revision 19868)
+++ source/blender/python/api2_2x/Window.c (working copy)
@@ -954,9 +954,11 @@
 				enter_editmode(0);
 			}
 		} else if( G.obedit ) {
-			if( undo_str_len > 63 )
-				undo_str[63] = '\0';	/* 64 is max */
-			BIF_undo_push( undo_str ); /* This checks user undo settings */
+			if( do_undo ) {
+				if( undo_str_len > 63 )
+					undo_str[63] = '\0';	/* 64 is max */
+				BIF_undo_push( undo_str ); /* This checks user undo settings */
+			}
 			exit_editmode( EM_FREEDATA );
 
 			//update armatures