diff --git a/types/webmidi/tsconfig.json b/types/webmidi/tsconfig.json
index 9598fd41ad..f804813d52 100644
--- a/types/webmidi/tsconfig.json
+++ b/types/webmidi/tsconfig.json
@@ -7,7 +7,7 @@
             "dom"
         ],
         "noImplicitAny": true,
-        "noImplicitThis": false,
+        "noImplicitThis": true,
         "strictNullChecks": true,
         "strictFunctionTypes": true,
         "baseUrl": "../",