diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py
index 6fc0c2296b..98797c37df 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -268,13 +268,15 @@ class MatrixFederationHttpClient(object):
         """
         Signs a request by adding an Authorization header to headers_dict
         Args:
-            destination (bytes): The desination home server of the request. May be None if the
-                destination is an identity server, in which case destination_is must be non-null.
+            destination (bytes): The desination home server of the request. May be None
+                if the destination is an identity server, in which case destination_is
+                must be non-null.
             method (bytes): The HTTP method of the request
             url_bytes (bytes): The URI path of the request
             headers_dict (dict): Dictionary of request headers to append to
             content (bytes): The body of the request
-            destination_is (bytes): As 'destination', but if the destination is an identity server
+            destination_is (bytes): As 'destination', but if the destination is an
+                identity server
 
         Returns:
             None