diff --git a/jwt/jwks_client.py b/jwt/jwks_client.py
index f4980e69..707724e5 100644
--- a/jwt/jwks_client.py
+++ b/jwt/jwks_client.py
@@ -53,5 +53,5 @@ def get_signing_key_from_jwt(self, token):
         unverified = decode_token(
             token, complete=True, options={"verify_signature": False}
         )
-        header = unverified.get("header")
+        header = unverified["header"]
         return self.get_signing_key(header.get("kid"))