diff --git a/types/chai-string/index.d.ts b/types/chai-string/index.d.ts
index bc990104be..fcf0fb9c23 100644
--- a/types/chai-string/index.d.ts
+++ b/types/chai-string/index.d.ts
@@ -49,4 +49,5 @@ declare global {
 }
 
 declare function chaiString(chai: any, utils: any): void;
+declare namespace chaiString { }
 export = chaiString;