diff --git a/README.md b/README.md
index 823778c..da20785 100644
--- a/README.md
+++ b/README.md
@@ -61,7 +61,7 @@ This is a modified edition of the NPM packages [`url-regex-safe`](https://www.np
 ## 🧩 APIs
 
 - ```ts
-  function urlRegExp(options?: URLRegExpOptions): RegExp;
+  function urlRegExp(options?: URLRegExpOptions & { returnString?: false; }): RegExp;
   function urlRegExp(options: URLRegExpOptions & { returnString: true; }): string;
   ```
 
diff --git a/mod.ts b/mod.ts
index ebe36a1..e257df5 100644
--- a/mod.ts
+++ b/mod.ts
@@ -73,7 +73,7 @@ export interface URLRegExpOptions {
 	 */
 	trailingPeriod?: boolean;
 }
-export function urlRegExp(options?: URLRegExpOptions): RegExp;
+export function urlRegExp(options?: URLRegExpOptions & { returnString?: false; }): RegExp;
 export function urlRegExp(options: URLRegExpOptions & { returnString: true; }): string;
 export function urlRegExp(options: URLRegExpOptions = {}): string | RegExp {
 	const {