diff --git a/acme/acme/jose/jws.py b/acme/acme/jose/jws.py
index 8fa8d7670..5f446e4b1 100644
--- a/acme/acme/jose/jws.py
+++ b/acme/acme/jose/jws.py
@@ -222,7 +222,8 @@ class Signature(json_util.JSONObjectWithFields):
 
         protected_params = {}
         for header in protect:
-            protected_params[header] = header_params.pop(header)
+            if header in header_params:
+                protected_params[header] = header_params.pop(header)
         if protected_params:
             # pylint: disable=star-args
             protected = cls.header_cls(**protected_params).json_dumps()
diff --git a/acme/acme/jws.py b/acme/acme/jws.py
index 79e96edcb..f9b81749a 100644
--- a/acme/acme/jws.py
+++ b/acme/acme/jws.py
@@ -49,6 +49,6 @@ class JWS(jose.JWS):
         # jwk field if kid is not provided.
         include_jwk = kid is None
         return super(JWS, cls).sign(payload, key=key, alg=alg,
-                                    protect=frozenset(['nonce', 'url', 'kid']),
+                                    protect=frozenset(['nonce', 'url', 'kid', 'jwk', 'alg']),
                                     nonce=nonce, url=url, kid=kid,
                                     include_jwk=include_jwk)