diff --git a/client/netwrapper.py b/client/netwrapper.py
index a4246dd..8671fd1 100644
--- a/client/netwrapper.py
+++ b/client/netwrapper.py
@@ -32,7 +32,8 @@ class NetWrapper:
         return encrypted_msg
 
     def signRSAHeader(self, type: str, extradata: dict) -> (bytes, bytes):
-        header = json.dumps({'type': type, 'source': self.network.own_addr}.update(extradata)).encode('UTF-8')
+        mandatory = {'type': type, 'source': self.network.own_addr}
+        header = json.dumps({**mandatory, **extradata}).encode('UTF-8')
         h = SHA512.new(header)
         headersignature = pkcs1_15.new(self.privateKey).sign(h)
         return header, headersignature