diff --git a/u2flib_server/attestation/matchers.py b/u2flib_server/attestation/matchers.py
index 39a3645..2a6fd0d 100644
--- a/u2flib_server/attestation/matchers.py
+++ b/u2flib_server/attestation/matchers.py
@@ -26,6 +26,7 @@
 # POSSIBILITY OF SUCH DAMAGE.
 
 from cryptography.x509 import ExtensionNotFound, ObjectIdentifier
+from binascii import a2b_hex
 
 
 __all__ = [
@@ -72,7 +73,7 @@ def matches(self, certificate, parameters={}):
 
         if isinstance(match_value, dict):
             if match_value['type'] == 'hex':
-                match_value = bytes.fromhex(match_value['value'])
+                match_value = a2b_hex(match_value['value'])
             else:
                 return False