diff --git a/synapse/rest/client/v2_alpha/notifications.py b/synapse/rest/client/v2_alpha/notifications.py
index ec170109f..66583d677 100644
--- a/synapse/rest/client/v2_alpha/notifications.py
+++ b/synapse/rest/client/v2_alpha/notifications.py
@@ -88,7 +88,7 @@ class NotificationsServlet(RestServlet):
                     pa["topological_ordering"], pa["stream_ordering"]
                 )
             returned_push_actions.append(returned_pa)
-            next_token = pa["stream_ordering"]
+            next_token = str(pa["stream_ordering"])
 
         defer.returnValue((200, {
             "notifications": returned_push_actions,