diff --git a/cryptography/hazmat/backends/commoncrypto/backend.py b/cryptography/hazmat/backends/commoncrypto/backend.py
index ee2e000..7193f1d 100644
--- a/cryptography/hazmat/backends/commoncrypto/backend.py
+++ b/cryptography/hazmat/backends/commoncrypto/backend.py
@@ -148,7 +148,7 @@
             (CFB, self._lib.kCCModeCFB),
             (OFB, self._lib.kCCModeOFB),
             (CTR, self._lib.kCCModeCTR),
-            (GCM, self._lib.kCCModeGCM)
+            (GCM, self._lib.kCCModeGCM),
         ]:
             self._register_cipher_adapter(
                 AES,