diff --git a/src/serve-static.ts b/src/serve-static.ts
index a2c2dd0..5de5639 100644
--- a/src/serve-static.ts
+++ b/src/serve-static.ts
@@ -149,8 +149,8 @@ export const serveStatic = <E extends Env = any>(
     c.header('Date', stats.birthtime.toUTCString())
 
     const parts = range.replace(/bytes=/, '').split('-', 2)
-    const start = parts[0] ? parseInt(parts[0], 10) : 0
-    let end = parts[1] ? parseInt(parts[1], 10) : stats.size - 1
+    const start = parseInt(parts[0], 10) || 0
+    let end = parseInt(parts[1], 10) || size - 1
     if (size < end - start + 1) {
       end = size - 1
     }
diff --git a/test/serve-static.test.ts b/test/serve-static.test.ts
index af93429..76e72e0 100644
--- a/test/serve-static.test.ts
+++ b/test/serve-static.test.ts
@@ -166,6 +166,13 @@ describe('Serve Static Middleware', () => {
     expect(res.text).toBe('This is plain.txt')
   })
 
+  it('Should handle invalid range header gracefully without NaN error', async () => {
+    const res = await request(server).get('/static/plain.txt').set('range', 'hello')
+    expect(res.status).toBe(206)
+    expect(res.headers['content-length']).toBe('17')
+    expect(res.headers['content-range']).toBe('bytes 0-16/17')
+  })
+
   it('Should handle the `onNotFound` option', async () => {
     const res = await request(server).get('/on-not-found/foo.txt')
     expect(res.status).toBe(404)