diff --git a/distribution/openrct2.d.ts b/distribution/openrct2.d.ts
index 6a554573a4..798635f3a2 100644
--- a/distribution/openrct2.d.ts
+++ b/distribution/openrct2.d.ts
@@ -811,7 +811,7 @@ declare global {
         maxHeight?: number;
         widgets?: Widget[];
         colours?: number[];
-        tabs: WindowTabDesc[];
+        tabs?: WindowTabDesc[];
 
         onClose?: () => void;
         onUpdate?: () => void;