diff --git a/content/.well-known/matrix/client b/content/.well-known/matrix/client
index ed726e2421..9bbf872194 100644
--- a/content/.well-known/matrix/client
+++ b/content/.well-known/matrix/client
@@ -4,5 +4,8 @@
     },
     "m.identity_server": {
         "base_url": "https://vector.im"
+    },
+    "org.matrix.msc3575.proxy": {
+        "url": "https://slidingsync.lab.matrix.org"
     }
 }