diff --git a/synapse/appservice/api.py b/synapse/appservice/api.py
index 9cce4e097..15ac1e27f 100644
--- a/synapse/appservice/api.py
+++ b/synapse/appservice/api.py
@@ -41,7 +41,7 @@ class ApplicationServiceApi(SimpleHttpClient):
             response = yield self.get_json(uri, {
                 "access_token": service.hs_token
             })
-            if response:  # just an empty json object
+            if response is not None:  # just an empty json object
                 defer.returnValue(True)
         except CodeMessageException as e:
             if e.code == 404:
@@ -60,13 +60,13 @@ class ApplicationServiceApi(SimpleHttpClient):
             response = yield self.get_json(uri, {
                 "access_token": service.hs_token
             })
-            if response:  # just an empty json object
+            if response is not None:  # just an empty json object
                 defer.returnValue(True)
         except CodeMessageException as e:
+            logger.warning("query_alias to %s received %s", uri, e.code)
             if e.code == 404:
                 defer.returnValue(False)
                 return
-            logger.warning("query_alias to %s received %s", uri, e.code)
         except Exception as ex:
             logger.warning("query_alias to %s threw exception %s", uri, ex)
         defer.returnValue(False)
diff --git a/synapse/handlers/appservice.py b/synapse/handlers/appservice.py
index 5071a12eb..8591a77bf 100644
--- a/synapse/handlers/appservice.py
+++ b/synapse/handlers/appservice.py
@@ -124,15 +124,15 @@ class ApplicationServicesHandler(object):
             namedtuple: with keys "room_id" and "servers" or None if no
             association can be found.
         """
-        room_alias = room_alias.to_string()
+        room_alias_str = room_alias.to_string()
         alias_query_services = yield self._get_services_for_event(
             event=None,
             restrict_to=ApplicationService.NS_ALIASES,
-            alias_list=[room_alias]
+            alias_list=[room_alias_str]
         )
         for alias_service in alias_query_services:
             is_known_alias = yield self.appservice_api.query_alias(
-                alias_service, room_alias
+                alias_service, room_alias_str
             )
             if is_known_alias:
                 # the alias exists now so don't query more ASes.
diff --git a/synapse/handlers/directory.py b/synapse/handlers/directory.py
index 22c6391a1..87bc12c98 100644
--- a/synapse/handlers/directory.py
+++ b/synapse/handlers/directory.py
@@ -64,8 +64,11 @@ class DirectoryHandler(BaseHandler):
         # association creation for human users
         # TODO(erikj): Do user auth.
 
-        is_claimed = yield self.is_alias_exclusive_to_appservices(room_alias)
-        if is_claimed:
+        can_create = yield self.can_modify_alias(
+            room_alias,
+            user_id=user_id
+        )
+        if not can_create:
             raise SynapseError(
                 400, "This alias is reserved by an application service.",
                 errcode=Codes.EXCLUSIVE
@@ -91,8 +94,11 @@ class DirectoryHandler(BaseHandler):
 
         # TODO Check if server admin
 
-        is_claimed = yield self.is_alias_exclusive_to_appservices(room_alias)
-        if is_claimed:
+        can_delete = yield self.can_modify_alias(
+            room_alias,
+            user_id=user_id
+        )
+        if not can_delete:
             raise SynapseError(
                 400, "This alias is reserved by an application service.",
                 errcode=Codes.EXCLUSIVE
@@ -228,9 +234,14 @@ class DirectoryHandler(BaseHandler):
         defer.returnValue(result)
 
     @defer.inlineCallbacks
-    def is_alias_exclusive_to_appservices(self, alias):
+    def can_modify_alias(self, alias, user_id=None):
         services = yield self.store.get_app_services()
         interested_services = [
             s for s in services if s.is_interested_in_alias(alias.to_string())
         ]
-        defer.returnValue(len(interested_services) > 0)
+        for service in interested_services:
+            if user_id == service.sender:
+                # this user IS the app service
+                defer.returnValue(True)
+                return
+        defer.returnValue(len(interested_services) == 0)