diff --git a/js/background.js b/js/background.js
index d05e22e..4bae54b 100644
--- a/js/background.js
+++ b/js/background.js
@@ -63,10 +63,11 @@ var uBOScope = { // jshint ignore:line
     dtpAssetKey: 'disconnect-tracking-protection',
     reAuthorityFromURI: /^(?:[^:\/?#]+:)?(\/\/[^\/?#]+)/,
     reCommonHostnameFromURL: /^https?:\/\/([0-9a-z_][0-9a-z._-]*[0-9a-z])\//,
-    reHostFromAuthority: /^(?:[^@]*@)?([0-9a-z._-]+)(?::\d*)?$/i,
+    reHostFromAuthority: /^(?:[^@]*@)?([^:]+)(?::\d*)?$/,
     reHostFromNakedAuthority: /^[0-9a-z._-]+[0-9a-z]$/i,
     reIPAddressNaive: /^\d+\.\d+\.\d+\.\d+$|^\[[\da-zA-Z:]+\]$/,
     reIPv6FromAuthority: /^(?:[^@]*@)?(\[[0-9a-f:]+\])(?::\d*)?$/i,
+    reMustNormalizeHostname: /[^0-9a-z._-]/,
     settings: {
         daysBefore: 30,
         heatmapHue: 0,
diff --git a/js/start.js b/js/start.js
index 938df64..f9fc85f 100644
--- a/js/start.js
+++ b/js/start.js
@@ -65,29 +65,27 @@ uBOScope.getDoY.dayCountLeap = [ 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 30
 
 uBOScope.hostnameFromURI = function(uri) {
     let matches = this.reCommonHostnameFromURL.exec(uri);
-    if ( matches ) {
-        return matches[1];
-    }
+    if ( matches !== null ) { return matches[1]; }
     matches = this.reAuthorityFromURI.exec(uri);
-    if ( !matches ) { return ''; }
+    if ( matches === null ) { return ''; }
     const authority = matches[1].slice(2);
     // Assume very simple authority (most common case for µBlock)
     if ( this.reHostFromNakedAuthority.test(authority) ) {
         return authority.toLowerCase();
     }
     matches = this.reHostFromAuthority.exec(authority);
-    if ( !matches ) {
+    if ( matches === null ) {
         matches = this.reIPv6FromAuthority.exec(authority);
-        if ( !matches ) { return ''; }
+        if ( matches === null ) { return ''; }
     }
-    // http://en.wikipedia.org/wiki/FQDN
-    // Also:
-    // - https://github.com/gorhill/uBlock/issues/1559
     let hostname = matches[1];
     while ( hostname.endsWith('.') ) {
         hostname = hostname.slice(0, -1);
     }
-    return hostname.toLowerCase();
+    if ( this.reMustNormalizeHostname.test(hostname) ) {
+        hostname = punycode.toASCII(hostname.toLowerCase());
+    }
+    return hostname;
 };
 
 /******************************************************************************/