diff --git a/packages/docusaurus/package.json b/packages/docusaurus/package.json
index df1969491191..219ba059a8be 100644
--- a/packages/docusaurus/package.json
+++ b/packages/docusaurus/package.json
@@ -74,6 +74,7 @@
     "inquirer": "^7.2.0",
     "is-root": "^2.1.0",
     "lodash": "^4.5.2",
+    "lodash.flatmap": "^4.5.0",
     "lodash.has": "^4.5.2",
     "lodash.isplainobject": "^4.0.6",
     "lodash.isstring": "^4.0.1",