diff --git a/setup.py b/setup.py
index 85e40c9..daa59d8 100644
--- a/setup.py
+++ b/setup.py
@@ -33,7 +33,7 @@
     if 'MACOSX_DEPLOYMENT_TARGET' not in os.environ:
         current_system = LooseVersion(platform.mac_ver()[0])
         python_target = LooseVersion(
-            get_config_var('MACOSX_DEPLOYMENT_TARGET'))
+            str(get_config_var('MACOSX_DEPLOYMENT_TARGET')))
         if python_target < '10.9' and current_system >= '10.9':
             os.environ['MACOSX_DEPLOYMENT_TARGET'] = '10.9'