diff --git a/lib/tfw/crypto.py b/lib/tfw/crypto.py
index 05f1daa..562420b 100644
--- a/lib/tfw/crypto.py
+++ b/lib/tfw/crypto.py
@@ -21,6 +21,7 @@ def message_checksum(message):
 
 
 def sign_message(key, message):
+    message.pop('scope', None)
     message.pop('signature', None)
     signature = message_signature(key, message)
     message['signature'] = b64encode(signature).decode()
@@ -31,6 +32,7 @@ def message_signature(key, message):
 
 
 def verify_message(key, message):
+    message.pop('scope', None)
     message = deepcopy(message)
     try:
         signature_b64 = message.pop('signature')