diff --git a/index.js b/index.js
index 134dec9..ba9979e 100644
--- a/index.js
+++ b/index.js
@@ -160,7 +160,7 @@ function serialize (cmpts, opts) {
     }
 
     if (authority === undefined) {
-      s = s.replace(/^\/\//, '/%2F') // don't allow the path to start with "//"
+      s = s.replace(/^\/\//u, '/%2F') // don't allow the path to start with "//"
     }
 
     uriTokens.push(s)
@@ -178,7 +178,7 @@ function serialize (cmpts, opts) {
   return uriTokens.join('')
 }
 
-const hexLookUp = Array.from({ length: 127 }, (v, k) => /[^!"$&'()*+,.;=_`a-z{}~-]/.test(String.fromCharCode(k)))
+const hexLookUp = Array.from({ length: 127 }, (v, k) => /[^!"$&'()*+,\-.;=_`a-z{}~]/u.test(String.fromCharCode(k)))
 
 function nonSimpleDomain (value) {
   let code = 0
@@ -191,7 +191,7 @@ function nonSimpleDomain (value) {
   return false
 }
 
-const URI_PARSE = /^(?:([^:/?#]+):)?(?:\/\/((?:([^/?#@]*)@)?(\[[^/?#\]]+\]|[^/?#:]*)(?::(\d*))?))?([^?#]*)(?:\?([^#]*))?(?:#((?:.|\n|\r)*))?/i
+const URI_PARSE = /^(?:([^#/:?]+):)?(?:\/\/((?:([^#/?@]*)@)?(\[[^#/?\]]+\]|[^#/:?]*)(?::(\d*))?))?([^#?]*)(?:\?([^#]*))?(?:#((?:.|[\n\r])*))?/u
 
 function parse (uri, opts) {
   const options = Object.assign({}, opts)
diff --git a/lib/schemes.js b/lib/schemes.js
index c5cd478..45d06fe 100644
--- a/lib/schemes.js
+++ b/lib/schemes.js
@@ -1,7 +1,7 @@
 'use strict'
 
-const UUID_REG = /^[0-9a-fA-F]{8}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{12}$/
-const URN_REG = /([A-Za-z0-9][A-Za-z0-9-]{0,31}):((?:[A-Za-z0-9()+,\-.:=@;$_!*']|%[0-9A-Fa-f]{2})+)/
+const UUID_REG = /^[\da-f]{8}\b-[\da-f]{4}\b-[\da-f]{4}\b-[\da-f]{4}\b-[\da-f]{12}$/iu
+const URN_REG = /([\da-z][\d\-a-z]{0,31}):((?:[\w!$'()*+,\-.:;=@]|%[\da-f]{2})+)/iu
 
 function isSecure (wsComponents) {
   return typeof wsComponents.secure === 'boolean' ? wsComponents.secure : String(wsComponents.scheme).toLowerCase() === 'wss'
diff --git a/lib/utils.js b/lib/utils.js
index 0716ab9..78134c6 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -4,7 +4,7 @@ const { HEX } = require('./scopedChars')
 
 function normalizeIPv4 (host) {
   if (findToken(host, '.') < 3) { return { host, isIPV4: false } }
-  const matches = host.match(/^(\b25[0-5]|\b2[0-4][0-9]|\b[01]?[0-9][0-9]?)(\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/) || []
+  const matches = host.match(/^(\b[01]?\d{1,2}|\b2[0-4]\d|\b25[0-5])(\.([01]?\d{1,2}|2[0-4]\d|25[0-5])){3}$/u) || []
   const [address] = matches
   if (address) {
     return { host: stripLeadingZeros(address, '.'), isIPV4: true }
@@ -138,10 +138,10 @@ function findToken (str, token) {
   return ind
 }
 
-const RDS1 = /^\.\.?\//
-const RDS2 = /^\/\.(\/|$)/
-const RDS3 = /^\/\.\.(\/|$)/
-const RDS5 = /^\/?(?:.|\n)*?(?=\/|$)/
+const RDS1 = /^\.\.?\//u
+const RDS2 = /^\/\.(?:\/|$)/u
+const RDS3 = /^\/\.\.(?:\/|$)/u
+const RDS5 = /^\/?(?:.|\n)*?(?=\/|$)/u
 
 function removeDotSegments (input) {
   const output = []