diff --git a/types/mailparser/tsconfig.json b/types/mailparser/tsconfig.json
index dea8c41473..35da481b34 100644
--- a/types/mailparser/tsconfig.json
+++ b/types/mailparser/tsconfig.json
@@ -6,7 +6,7 @@
         ],
         "noImplicitAny": true,
         "noImplicitThis": true,
-        "strictNullChecks": false,
+        "strictNullChecks": true,
         "strictFunctionTypes": true,
         "baseUrl": "../",
         "typeRoots": [