diff --git setup.py setup.py
--- setup.py
+++ setup.py
@@ -58,7 +58,12 @@ def get_sdk_level(sdk):
     assert sdk.startswith('MacOSX')
     assert sdk.endswith('.sdk')
     sdk =  sdk[6:-4]
-    return sdk
+    if sdk == '':
+        return get_os_level()
+    elif '.' not in sdk:
+        return sdk + '.0'
+    else:
+        return sdk
 
 
 
