diff --git a/fido2/mds3.py b/fido2/mds3.py
index bdcc3d8..30c253c 100644
--- a/fido2/mds3.py
+++ b/fido2/mds3.py
@@ -428,7 +428,7 @@ def ca_lookup(self, result, auth_data):
 
             # Figure out which root to use
             if not entry.metadata_statement:
-                logging.warn("Matched entry has no metadata_statement, can't validate!")
+                logging.warning("Matched entry has no metadata_statement, can't validate!")
                 return None
 
             issuer = x509.load_der_x509_certificate(