diff --git a/index.d.ts b/index.d.ts
index 2901ace..0dbfb0e 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -18,6 +18,7 @@ declare module '@namecheap/error-extender' {
         defaultMessage?: string;
         defaultData?: DataType;
         parent?: Error;
+        inverse?: boolean;
     }
 
     export default function <DataType = any>(errType: string, config?: ExtendConfig<DataType>): ExtendedError<DataType>;