diff --git a/src/client/client.test.ts b/src/client/client.test.ts
index defedcde4..141e3c97c 100644
--- a/src/client/client.test.ts
+++ b/src/client/client.test.ts
@@ -885,6 +885,20 @@ describe('Use custom fetch (app.request) method', () => {
     const res = await client.search.$get()
     expect(res.ok).toBe(true)
   })
+
+  it.each([false, 0, '', null])('Should send falsy JSON value: %j', async (json) => {
+    const app = new Hono().post(
+      '/json',
+      validator('json', (value) => value as boolean | number | string | null),
+      (c) => c.json(c.req.valid('json'))
+    )
+    const client = hc<typeof app>('', { fetch: app.request })
+
+    const res = await client.json.$post({ json })
+
+    expect(res.status).toBe(200)
+    expect(await res.json()).toBe(json)
+  })
 })
 
 describe('Optional parameters in JSON response', () => {
diff --git a/src/client/client.ts b/src/client/client.ts
index 0a6144830..1ce6d60a1 100644
--- a/src/client/client.ts
+++ b/src/client/client.ts
@@ -78,7 +78,7 @@ class ClientRequestImpl {
         this.rBody = form
       }
 
-      if (args.json) {
+      if (args.json !== undefined) {
         this.rBody = JSON.stringify(args.json)
         this.cType = 'application/json'
       }
diff --git a/src/middleware/cors/index.test.ts b/src/middleware/cors/index.test.ts
index 9ea184c70..ee9efdf2d 100644
--- a/src/middleware/cors/index.test.ts
+++ b/src/middleware/cors/index.test.ts
@@ -382,6 +382,17 @@ describe('CORS by Middleware', () => {
     expect(res2.headers.get('Access-Control-Allow-Methods')).toBe('GET,HEAD')
   })
 
+  it('Does not set allow methods when function returns an empty array', async () => {
+    for (const allowMethods of [() => [], async () => []]) {
+      const app = new Hono()
+      app.use(cors({ allowMethods }))
+
+      const res = await app.request('http://localhost/', { method: 'OPTIONS' })
+
+      expect(res.headers.get('Access-Control-Allow-Methods')).toBeNull()
+    }
+  })
+
   it('Emits the wildcard, not the reflected origin, when credentials is true with wildcard origin', async () => {
     const res = await app.request('http://localhost/api10/abc', {
       headers: {
diff --git a/src/middleware/cors/index.ts b/src/middleware/cors/index.ts
index e4a45400a..1ea2e012a 100644
--- a/src/middleware/cors/index.ts
+++ b/src/middleware/cors/index.ts
@@ -69,6 +69,9 @@ export const cors = (options?: CORSOptions): MiddlewareHandler => {
     ...options,
   } satisfies CORSOptions
 
+  const exposeHeadersStr = opts.exposeHeaders?.length ? opts.exposeHeaders.join(',') : undefined
+  const allowHeadersStr = opts.allowHeaders?.length ? opts.allowHeaders.join(',') : undefined
+
   const findAllowOrigin = ((optsOrigin) => {
     if (typeof optsOrigin === 'string') {
       if (optsOrigin === '*') {
@@ -85,11 +88,12 @@ export const cors = (options?: CORSOptions): MiddlewareHandler => {
 
   const findAllowMethods = ((optsAllowMethods) => {
     if (typeof optsAllowMethods === 'function') {
-      return optsAllowMethods
+      return async (origin: string, c: Context) => (await optsAllowMethods(origin, c)).join(',')
     } else if (Array.isArray(optsAllowMethods)) {
-      return () => optsAllowMethods
+      const methodsStr = optsAllowMethods.join(',')
+      return () => methodsStr
     } else {
-      return () => []
+      return () => ''
     }
   })(opts.allowMethods)
 
@@ -107,8 +111,8 @@ export const cors = (options?: CORSOptions): MiddlewareHandler => {
       set('Access-Control-Allow-Credentials', 'true')
     }
 
-    if (opts.exposeHeaders?.length) {
-      set('Access-Control-Expose-Headers', opts.exposeHeaders.join(','))
+    if (exposeHeadersStr) {
+      set('Access-Control-Expose-Headers', exposeHeadersStr)
     }
 
     if (c.req.method === 'OPTIONS') {
@@ -121,19 +125,22 @@ export const cors = (options?: CORSOptions): MiddlewareHandler => {
       }
 
       const allowMethods = await findAllowMethods(c.req.header('origin') || '', c)
-      if (allowMethods.length) {
-        set('Access-Control-Allow-Methods', allowMethods.join(','))
+      if (allowMethods) {
+        set('Access-Control-Allow-Methods', allowMethods)
       }
 
-      let headers = opts.allowHeaders
-      if (!headers?.length) {
+      let headersStr = allowHeadersStr
+      if (!headersStr) {
         const requestHeaders = c.req.header('Access-Control-Request-Headers')
         if (requestHeaders) {
-          headers = requestHeaders.split(',').map((h) => h.trim())
+          headersStr = requestHeaders
+            .split(',')
+            .map((h) => h.trim())
+            .join(',')
         }
       }
-      if (headers?.length) {
-        set('Access-Control-Allow-Headers', headers.join(','))
+      if (headersStr) {
+        set('Access-Control-Allow-Headers', headersStr)
         c.res.headers.append('Vary', 'Access-Control-Request-Headers')
       }
 
diff --git a/src/utils/url.test.ts b/src/utils/url.test.ts
index 7274d5db7..2fcd70d72 100644
--- a/src/utils/url.test.ts
+++ b/src/utils/url.test.ts
@@ -253,6 +253,7 @@ describe('url', () => {
         '/api/:version/animal',
         '/api/:version/animal/:type',
       ])
+      expect(checkOptionalParameter('/api/:id{[0-9]?}?')).toEqual(['/api', '/api/:id{[0-9]?}'])
     })
   })
 
diff --git a/src/utils/url.ts b/src/utils/url.ts
index ea92ff935..124936482 100644
--- a/src/utils/url.ts
+++ b/src/utils/url.ts
@@ -187,13 +187,13 @@ export const checkOptionalParameter = (path: string): string[] | null => {
     if (segment !== '' && !/\:/.test(segment)) {
       basePath += '/' + segment
     } else if (/\:/.test(segment)) {
-      if (/\?/.test(segment)) {
+      if (segment.charCodeAt(segment.length - 1) === 63) {
         if (results.length === 0 && basePath === '') {
           results.push('/')
         } else {
           results.push(basePath)
         }
-        const optionalSegment = segment.replace('?', '')
+        const optionalSegment = segment.slice(0, -1)
         basePath += '/' + optionalSegment
         results.push(basePath)
       } else {