diff --git a/synapse/appservice/api.py b/synapse/appservice/api.py
index d28a9dff0..632dc1a4f 100644
--- a/synapse/appservice/api.py
+++ b/synapse/appservice/api.py
@@ -29,6 +29,9 @@ logger = logging.getLogger(__name__)
 HOUR_IN_MS = 60 * 60 * 1000
 
 
+APP_SERVICE_PREFIX = "/_matrix/app/unstable"
+
+
 def _is_valid_3pe_result(r, field):
     if not isinstance(r, dict):
         return False
@@ -103,16 +106,22 @@ class ApplicationServiceApi(SimpleHttpClient):
     @defer.inlineCallbacks
     def query_3pe(self, service, kind, protocol, fields):
         if kind == ThirdPartyEntityKind.USER:
-            uri = "%s/thirdparty/user/%s" % (service.url, urllib.quote(protocol))
+            fragment = "user"
             required_field = "userid"
         elif kind == ThirdPartyEntityKind.LOCATION:
-            uri = "%s/thirdparty/location/%s" % (service.url, urllib.quote(protocol))
+            fragment = "location"
             required_field = "alias"
         else:
             raise ValueError(
                 "Unrecognised 'kind' argument %r to query_3pe()", kind
             )
 
+        uri = "%s%s/thirdparty/%s/%s" % (
+            service.url,
+            APP_SERVICE_PREFIX,
+            fragment,
+            urllib.quote(protocol)
+        )
         try:
             response = yield self.get_json(uri, fields)
             if not isinstance(response, list):
@@ -140,7 +149,11 @@ class ApplicationServiceApi(SimpleHttpClient):
     def get_3pe_protocol(self, service, protocol):
         @defer.inlineCallbacks
         def _get():
-            uri = "%s/thirdparty/protocol/%s" % (service.url, urllib.quote(protocol))
+            uri = "%s%s/thirdparty/protocol/%s" % (
+                service.url,
+                APP_SERVICE_PREFIX,
+                urllib.quote(protocol)
+            )
             try:
                 defer.returnValue((yield self.get_json(uri, {})))
             except Exception as ex: