diff --git a/demo/package-lock.json b/demo/package-lock.json
index 7dcb49bb..6f610bae 100644
--- a/demo/package-lock.json
+++ b/demo/package-lock.json
@@ -9,7 +9,7 @@
       "version": "0.0.0",
       "dependencies": {
         "@ably/chat": "file:..",
-        "ably": "^2.5.0",
+        "ably": "ably/ably-js#mutable-messages-with-submodule-test",
         "clsx": "^2.1.1",
         "nanoid": "^5.0.8",
         "react": "^18.3.1",
@@ -1699,8 +1699,7 @@
     },
     "node_modules/ably": {
       "version": "2.5.0",
-      "resolved": "https://registry.npmjs.org/ably/-/ably-2.5.0.tgz",
-      "integrity": "sha512-PgZk1gDO7K5p5QbTGAV6n2un6otbu91J8n+2Bv/sCoNmfFqyAtQFnj/dWpcJTC3kwbxX/E3kimZAgnSXeNG8dg==",
+      "resolved": "git+ssh://git@github.com/ably/ably-js.git#c5c99987920327cadf144fa3f7652c8f4672c6cd",
       "license": "Apache-2.0",
       "dependencies": {
         "@ably/msgpack-js": "^0.4.0",
diff --git a/demo/package.json b/demo/package.json
index a133f6c6..869be53c 100644
--- a/demo/package.json
+++ b/demo/package.json
@@ -14,7 +14,7 @@
   },
   "dependencies": {
     "@ably/chat": "file:..",
-    "ably": "^2.5.0",
+    "ably": "ably/ably-js#mutable-messages-with-submodule-test",
     "clsx": "^2.1.1",
     "nanoid": "^5.0.8",
     "react": "^18.3.1",