diff --git a/synapse/config/server.py b/synapse/config/server.py
index 395daa3c01..23c3d14013 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -108,17 +108,17 @@ class ServerConfig(Config):
             "federation_domain_whitelist", None
         )
 
-        # Optional proxy address for federation traffic
-        self.federation_request_gateway_addr = config.get(
-            "federation_request_gateway_addr", None
-        )
-
         # turn the whitelist into a hash for speed of lookup
         if federation_domain_whitelist is not None:
             self.federation_domain_whitelist = {}
             for domain in federation_domain_whitelist:
                 self.federation_domain_whitelist[domain] = True
 
+        # Optional proxy address for federation traffic
+        self.federation_request_gateway_addr = config.get(
+            "federation_request_gateway_addr", None
+        )
+
         if self.federation_request_gateway_addr is not None:
             # Ensure proxy address is correctly formatted
             if len(self.federation_request_gateway_addr.split(':')) != 2:
diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py
index 048bfa1870..92c70e3f0c 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -69,10 +69,11 @@ class ProxyMatrixFederationEndpointFactory(object):
     def __init__(self, hs):
         self.reactor = hs.get_reactor()
         self.tls_client_options_factory = hs.tls_client_options_factory
+        self.gateway_addr = hs.config.federation_request_gateway_addr
 
     def endpointForURI(self, uri):
         return matrix_federation_endpoint(
-            self.reactor, self.hs.config.federation_request_gateway_addr, timeout=10,
+            self.reactor, self.gateway_addr, timeout=10,
             tls_client_options_factory=None
         )
 
diff --git a/tests/utils.py b/tests/utils.py
index 08d6faa0a6..ed386f91cd 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -115,6 +115,7 @@ def default_config(name):
     config.email_enable_notifs = False
     config.block_non_admin_invites = False
     config.federation_domain_whitelist = None
+    config.federation_request_gateway_addr = None
     config.federation_rc_reject_limit = 10
     config.federation_rc_sleep_limit = 10
     config.federation_rc_sleep_delay = 100