diff --git a/src/Types/Params.ts b/src/Types/Params.ts
index 300c211..045e056 100644
--- a/src/Types/Params.ts
+++ b/src/Types/Params.ts
@@ -7,4 +7,4 @@
  * All values are strings and should be considered read-only, as they are
  * extracted by the router and should not be modified by application code.
  */
-export type Params = Record<string, string | undefined>;
+export type Params = Record<string, string>;
diff --git a/src/Utils/createRouteMatcher.ts b/src/Utils/createRouteMatcher.ts
index 90fc2a5..97f5477 100644
--- a/src/Utils/createRouteMatcher.ts
+++ b/src/Utils/createRouteMatcher.ts
@@ -35,7 +35,7 @@ export function createRouteMatcher(
         // 3b. Extract route params
         const params: Params = {};
         for (const [key, value] of Object.entries(result.pathname.groups)) {
-            params[key] = value;
+            params[key] = value ?? ''; // null → empty string
         }
 
         // 3c. Extract query parameters – keep duplicates as arrays