diff --git a/letsencrypt/le_util.py b/letsencrypt/le_util.py
index 112c90a6e..a5c1a26a1 100644
--- a/letsencrypt/le_util.py
+++ b/letsencrypt/le_util.py
@@ -222,6 +222,7 @@ def get_os_info():
             ["sw_vers", "-productVersion"],
             stdout=subprocess.PIPE
         ).communicate()[0]
+        os_ver = os_ver.partition(".")[0]
     elif os_type.startswith('freebsd'):
         # eg "9.3-RC3-p1"
         os_ver = os_ver.partition("-")[0]