diff --git a/packages/html-manager/package.json b/packages/html-manager/package.json
index 36b8e50c14..7272dfbc01 100644
--- a/packages/html-manager/package.json
+++ b/packages/html-manager/package.json
@@ -44,6 +44,7 @@
     "@jupyterlab/outputarea": "^3.0.0",
     "@jupyterlab/rendermime": "^3.0.0",
     "@jupyterlab/rendermime-interfaces": "^3.0.0",
+    "@lumino/messaging": "^1.3.3",
     "@lumino/widgets": "^1.11.1",
     "ajv": "^6.10.0",
     "jquery": "^3.1.1"