diff --git a/src/middleware/core.js b/src/middleware/core.js
index 9957929..3dc8718 100644
--- a/src/middleware/core.js
+++ b/src/middleware/core.js
@@ -6,6 +6,7 @@ const generateServerString = require("../utils/generateServerString.js");
 const serverHTTPErrorDescs = require("../res/httpErrorDescriptions.js");
 const fixNodeMojibakeURL = require("../utils/urlMojibakeFixer.js");
 const ipMatch = require("../utils/ipMatch.js");
+const matchHostname = require("../utils/matchHostname.js");
 const svrjsInfo = require("../../svrjs.json");
 const version = svrjsInfo.version;
 
@@ -14,29 +15,6 @@ if (!process.err5xxcounter) process.err5xxcounter = 0;
 if (!process.reqcounter) process.reqcounter = 0;
 
 module.exports = (req, res, logFacilities, config, next) => {
-  const matchHostname = (hostname) => {
-    if (typeof hostname == "undefined" || hostname == "*") {
-      return true;
-    } else if (
-      req.headers.host &&
-      hostname.indexOf("*.") == 0 &&
-      hostname != "*."
-    ) {
-      const hostnamesRoot = hostname.substring(2);
-      if (
-        req.headers.host == hostnamesRoot ||
-        (req.headers.host.length > hostnamesRoot.length &&
-          req.headers.host.indexOf("." + hostnamesRoot) ==
-            req.headers.host.length - hostnamesRoot.length - 1)
-      ) {
-        return true;
-      }
-    } else if (req.headers.host && req.headers.host == hostname) {
-      return true;
-    }
-    return false;
-  };
-
   config.generateServerString = () => {
     return generateServerString(config.exposeServerVersion);
   };
@@ -48,7 +26,7 @@ module.exports = (req, res, logFacilities, config, next) => {
       let vhostP = null;
       config.customHeadersVHost.every(function (vhost) {
         if (
-          matchHostname(vhost.host) &&
+          matchHostname(vhost.host, req.headers.host) &&
           ipMatch(vhost.ip, req.socket ? req.socket.localAddress : undefined)
         ) {
           vhostP = vhost;
@@ -398,7 +376,7 @@ module.exports = (req, res, logFacilities, config, next) => {
       if (
         list[_i].scode != errorCode ||
         !(
-          matchHostname(list[_i].host) &&
+          matchHostname(list[_i].host, req.headers.host) &&
           ipMatch(list[_i].ip, req.socket ? req.socket.localAddress : undefined)
         )
       ) {
diff --git a/src/middleware/rewriteURL.js b/src/middleware/rewriteURL.js
index 2402d74..edf236c 100644
--- a/src/middleware/rewriteURL.js
+++ b/src/middleware/rewriteURL.js
@@ -3,6 +3,7 @@ const url = require("url");
 const createRegex = require("../utils/createRegex.js");
 const ipMatch = require("../utils/ipMatch.js");
 const sanitizeURL = require("../utils/urlSanitizer.js");
+const matchHostname = require("../utils/matchHostname.js");
 
 module.exports = (req, res, logFacilities, config, next) => {
   try {
@@ -11,29 +12,6 @@ module.exports = (req, res, logFacilities, config, next) => {
     res.error(400);
   }
 
-  const matchHostname = (hostname) => {
-    if (typeof hostname == "undefined" || hostname == "*") {
-      return true;
-    } else if (
-      req.headers.host &&
-      hostname.indexOf("*.") == 0 &&
-      hostname != "*."
-    ) {
-      const hostnamesRoot = hostname.substring(2);
-      if (
-        req.headers.host == hostnamesRoot ||
-        (req.headers.host.length > hostnamesRoot.length &&
-          req.headers.host.indexOf("." + hostnamesRoot) ==
-            req.headers.host.length - hostnamesRoot.length - 1)
-      ) {
-        return true;
-      }
-    } else if (req.headers.host && req.headers.host == hostname) {
-      return true;
-    }
-    return false;
-  };
-
   // Handle URL rewriting
   const rewriteURL = (address, map, callback, _fileState, _mapBegIndex) => {
     let rewrittenURL = address;
@@ -71,7 +49,7 @@ module.exports = (req, res, logFacilities, config, next) => {
           tempRewrittenURL = address;
         }
         if (
-          matchHostname(mapEntry.host) &&
+          matchHostname(mapEntry.host, req.headers.host) &&
           ipMatch(
             mapEntry.ip,
             req.socket ? req.socket.localAddress : undefined,
diff --git a/src/utils/matchHostname.js b/src/utils/matchHostname.js
new file mode 100644
index 0000000..5638c07
--- /dev/null
+++ b/src/utils/matchHostname.js
@@ -0,0 +1,24 @@
+function matchHostname(hostname, reqHostname) {
+    if (typeof hostname == "undefined" || hostname == "*") {
+        return true;
+    } else if (
+        reqHostname &&
+        hostname.indexOf("*.") == 0 &&
+        hostname != "*."
+    ) {
+        const hostnamesRoot = hostname.substring(2);
+        if (
+            reqHostname == hostnamesRoot ||
+            (reqHostname.length > hostnamesRoot.length &&
+                reqHostname.indexOf("." + hostnamesRoot) ==
+                reqHostname.length - hostnamesRoot.length - 1)
+        ) {
+            return true;
+        }
+    } else if (reqHostname && reqHostname == hostname) {
+        return true;
+    }
+    return false;
+};
+
+module.exports = matchHostname;
\ No newline at end of file
diff --git a/tests/utils/matchHostname.test.js b/tests/utils/matchHostname.test.js
new file mode 100644
index 0000000..a57537c
--- /dev/null
+++ b/tests/utils/matchHostname.test.js
@@ -0,0 +1,51 @@
+const matchHostname = require('../../src/utils/matchHostname');
+
+describe('matchHostname', () => {
+  test('should return true if hostname is undefined', () => {
+    expect(matchHostname(undefined, 'example.com')).toBe(true);
+  });
+
+  test('should return true if hostname is "*"', () => {
+    expect(matchHostname('*', 'example.com')).toBe(true);
+  });
+
+  test('should return true if reqHostname matches hostname exactly', () => {
+    expect(matchHostname('example.com', 'example.com')).toBe(true);
+  });
+
+  test('should return false if reqHostname does not match hostname exactly', () => {
+    expect(matchHostname('example.com', 'example.org')).toBe(false);
+  });
+
+  test('should return true if hostname starts with "*." and reqHostname matches the root', () => {
+    expect(matchHostname('*.example.com', 'sub.example.com')).toBe(true);
+  });
+
+  test('should return false if hostname starts with "*." and reqHostname does not match the root', () => {
+    expect(matchHostname('*.example.com', 'example.org')).toBe(false);
+  });
+
+  test('should return true if hostname starts with "*." and reqHostname is the root', () => {
+    expect(matchHostname('*.example.com', 'example.com')).toBe(true);
+  });
+
+  test('should return false if hostname is "*."', () => {
+    expect(matchHostname('*.', 'example.com')).toBe(false);
+  });
+
+  test('should return false if reqHostname is undefined', () => {
+    expect(matchHostname('example.com', undefined)).toBe(false);
+  });
+
+  test('should return false if hostname does not start with "*." and reqHostname does not match', () => {
+    expect(matchHostname('sub.example.com', 'example.com')).toBe(false);
+  });
+
+  test('should return true if hostname starts with "*." and reqHostname matches the root with additional subdomains', () => {
+    expect(matchHostname('*.example.com', 'sub.sub.example.com')).toBe(true);
+  });
+
+  test('should return false if hostname starts with "*." and reqHostname does not match the root with additional subdomains', () => {
+    expect(matchHostname('*.example.com', 'sub.sub.example.org')).toBe(false);
+  });
+});