diff --git a/index.js b/index.js
index 72f30be..1e3024a 100644
--- a/index.js
+++ b/index.js
@@ -108,7 +108,7 @@ function fastifyCompress (fastify, opts, next) {
   next()
 }
 
-const defaultCompressibleTypes = /^text\/(?!event-stream)|(\+|\/)json(;|$)|(\+|\/)text(;|$)|(\+|\/)xml(;|$)|octet-stream(;|$)/
+const defaultCompressibleTypes = /^text\/(?!event-stream)|(?:\+|\/)json(?:;|$)|(?:\+|\/)text(?:;|$)|(?:\+|\/)xml(?:;|$)|octet-stream(?:;|$)/u
 
 function processCompressParams (opts) {
   /* istanbul ignore next */
@@ -453,6 +453,8 @@ function onDecompressError (request, params, encoding, error) {
   Object.assign(error, errorPayload)
 }
 
+const gzipAlias = /\*|x-gzip/gu
+
 function getEncodingHeader (encodings, request) {
   let header = request.headers['accept-encoding']
   if (header != null) {
@@ -460,7 +462,7 @@ function getEncodingHeader (encodings, request) {
       // consider the no-preference token as gzip for downstream compat
       // and x-gzip as an alias of gzip
       // ref.: [HTTP/1.1 RFC 7230 section 4.2.3](https://datatracker.ietf.org/doc/html/rfc7230#section-4.2.3)
-      .replace(/\*|x-gzip/g, 'gzip')
+      .replace(gzipAlias, 'gzip')
     return encodingNegotiator.negotiate(header, encodings)
   } else {
     return undefined
diff --git a/test/global-compress.test.js b/test/global-compress.test.js
index cc971e5..659e2b4 100644
--- a/test/global-compress.test.js
+++ b/test/global-compress.test.js
@@ -766,7 +766,7 @@ test('It should not compress :', async (t) => {
       t.plan(2)
 
       const fastify = Fastify()
-      await fastify.register(compressPlugin, { customTypes: /x-user-header$/ })
+      await fastify.register(compressPlugin, { customTypes: /x-user-header$/u })
 
       fastify.get('/', (request, reply) => {
         reply
@@ -1101,7 +1101,7 @@ test('It should not compress :', async (t) => {
       t.plan(2)
 
       const fastify = Fastify()
-      await fastify.register(compressPlugin, { customTypes: /x-user-header$/ })
+      await fastify.register(compressPlugin, { customTypes: /x-user-header$/u })
 
       fastify.get('/', (request, reply) => {
         reply
@@ -2445,7 +2445,7 @@ test('`Accept-Encoding` request header values :', async (t) => {
 test('It should compress data if `customTypes` is set and matches `Content-Type` reply header value', async (t) => {
   t.plan(2)
   const fastify = Fastify()
-  await fastify.register(compressPlugin, { customTypes: /x-user-header$/ })
+  await fastify.register(compressPlugin, { customTypes: /x-user-header$/u })
 
   fastify.get('/', (request, reply) => {
     reply