From 8bc3caeb37a0306b3eaad7413b8fbbef7043cb87 Mon Sep 17 00:00:00 2001
From: greymoth <246701683+greymoth-jp@users.noreply.github.com>
Date: Tue, 30 Jun 2026 15:55:43 +0900
Subject: [PATCH] fix: normalize NaN status to 500 in createError

---
 index.js     |  2 +-
 test/test.js | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/index.js b/index.js
index 82271f6..951a698 100644
--- a/index.js
+++ b/index.js
@@ -73,7 +73,7 @@ function createError () {
     deprecate('non-error status code; use only 4xx or 5xx status codes')
   }
 
-  if (typeof status !== 'number' ||
+  if (typeof status !== 'number' || isNaN(status) ||
     (!statuses.message[status] && (status < 400 || status >= 600))) {
     status = 500
   }
diff --git a/test/test.js b/test/test.js
index 7db9f16..9f11fa1 100644
--- a/test/test.js
+++ b/test/test.js
@@ -138,6 +138,28 @@ describe('createError(status)', function () {
       assert.strictEqual(this.error.statusCode, 599)
     })
   })
+
+  describe('when status is NaN', function () {
+    before(function () {
+      this.error = createError(NaN)
+    })
+
+    it('should have "message" property of "Internal Server Error"', function () {
+      assert.strictEqual(this.error.message, 'Internal Server Error')
+    })
+
+    it('should have "name" property of "InternalServerError"', function () {
+      assert.strictEqual(this.error.name, 'InternalServerError')
+    })
+
+    it('should have "status" property of 500', function () {
+      assert.strictEqual(this.error.status, 500)
+    })
+
+    it('should have "statusCode" property of 500', function () {
+      assert.strictEqual(this.error.statusCode, 500)
+    })
+  })
 })
 
 describe('createError(status, message)', function () {