diff --git a/slugify.d.ts b/slugify.d.ts
index ade1592..631886c 100644
--- a/slugify.d.ts
+++ b/slugify.d.ts
@@ -1,23 +1,43 @@
 declare module slugify {
   type ExtendArgs = {
     [key: string]: any;
-  }
+  };
 
-  export function extend (args: ExtendArgs): void;
+  export function extend(args: ExtendArgs): void;
 }
 
+/**
+ * @param string
+ * @param replacement replace spaces with replacement character, defaults to `-`
+ */
+declare function slugify(string: string, replacement?: string): string;
 declare function slugify(
   string: string,
-  options?:
-    | {
-        replacement?: string;
-        remove?: RegExp;
-        lower?: boolean;
-        strict?: boolean;
-        locale?: string;
-      }
-    | string,
-
+  options?: {
+    /**
+     * replace spaces with replacement character
+     * @default '-'
+     */
+    replacement?: string;
+    /**
+     * remove characters that match regex
+     */
+    remove?: RegExp;
+    /**
+     * convert to lower case
+     * @default false
+     */
+    lower?: boolean;
+    /**
+     * strip special characters except replacement
+     * @default false
+     */
+    strict?: boolean;
+    /**
+     * language code of the locale to use
+     */
+    locale?: string;
+  }
 ): string;
 
 export default slugify;