diff --git a/packages/govuk-frontend/tsconfig.build.json b/packages/govuk-frontend/tsconfig.build.json
index 1cad87c1ca..f69b767483 100644
--- a/packages/govuk-frontend/tsconfig.build.json
+++ b/packages/govuk-frontend/tsconfig.build.json
@@ -4,6 +4,7 @@
   "exclude": ["**/*.test.*"],
   "compilerOptions": {
     "lib": ["ESNext", "DOM"],
+    "strict": true,
     "target": "ES2015",
     "types": ["node"]
   }