diff --git a/helpers/Status.ts b/helpers/Status.ts
index 7619fcb..cae5bc5 100644
--- a/helpers/Status.ts
+++ b/helpers/Status.ts
@@ -62,7 +62,7 @@ export const enum Status {
 }
 
 
-export function getReasonPhrase(status: Status | number): string {
+export function getReasonPhrase(status: number): string {
     switch (status) {
         case Status.S100_Continue:
             return 'Continue';
diff --git a/routers/MaskRouter.ts b/routers/MaskRouter.ts
index 359162b..315a35c 100644
--- a/routers/MaskRouter.ts
+++ b/routers/MaskRouter.ts
@@ -143,7 +143,12 @@ export class MaskRouter extends Router implements IRouter {
                 };
 
                 const name = groups.name;
-                const defaultValue = groups.defaultValue ?? null;
+
+                const defaultValue = (v => {
+                    if (v !== null && v !== '') return v;
+                    return null;
+                })(groups.defaultValue?.trim() ?? null);
+
                 const expression = (v => {
                     if (v !== null) {
                         try {
diff --git a/routers/RouterList.ts b/routers/RouterList.ts
index fc15942..aa4bbbd 100644
--- a/routers/RouterList.ts
+++ b/routers/RouterList.ts
@@ -144,7 +144,7 @@ export class RouterList implements IRouter {
     }
 
 
-    setError(status: Status | number, serveResponse: ServeResponseType): void {
+    setError(status: number, serveResponse: ServeResponseType): void {
         if (Number.isInteger(status)) {
             throw new Error("Status must be integer.");
         }
@@ -153,7 +153,7 @@ export class RouterList implements IRouter {
     }
 
 
-    async getErrorReponse(status: Status | number, req: Request, params: Record<string, string> = {}): Promise<Response> {
+    async getErrorReponse(status: number, req: Request, params: Record<string, string> = {}): Promise<Response> {
         const serveResponse = this.#errors.get(status);
         const phrase = getReasonPhrase(status);
 
diff --git a/tests/MaskRouter.test.ts b/tests/MaskRouter.test.ts
index 91238cc..692cc35 100644
--- a/tests/MaskRouter.test.ts
+++ b/tests/MaskRouter.test.ts
@@ -151,6 +151,12 @@ Deno.test("MaskRouter::parseParams", async () => {
                 action: "default",
             },
         },
+        {
+            mask: "[<s= >]",
+            pathname: "",
+            expectation: {
+            },
+        },
     ];