diff --git a/CHANGELOG.md b/CHANGELOG.md
index 471a5711..e5bf2d8d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## Release 1.2.2
+
+* FIX: Race condition in handover to PWA code
+
 ## Release 1.2.1
 
 * UPDATE: Minor update to improve handover between local and PWA code
diff --git a/www/index.html b/www/index.html
index 6ed87d47..f2d58fac 100644
--- a/www/index.html
+++ b/www/index.html
@@ -59,7 +59,7 @@
             window.require = undefined;
             window.fs = requireNode('fs');
         } 
-        if ('serviceWorker' in navigator && /^http|ms-appx-web/.test(window.location.protocol)) {
+        if ('serviceWorker' in navigator && !/^ms-appx-web/i.test(window.location.protocol)) {
             console.log('Trying to activate Service Worker...');
             if (navigator.serviceWorker.controller) {
                 console.log('Service Worker is already active');
@@ -69,6 +69,8 @@
                     scope: "../"
                 }).then(function (reg) {
                     console.log("Service worker has been registered for scope: " + reg.scope);
+                }).catch(function (err) {
+                    console.err('Service worker could not be registered', err);
                 });
             }
         } else {
@@ -113,6 +115,7 @@
                     <div id="update" class="update">
                         <h3 style="margin-top:0;">Changes in version <span class="version">1.0</span></h3>
                         <ul style="padding-left: 15px;">
+                            <li>Critical update to prevent race condition in switch to PWA</li>
                             <li>Minor update to improve handover between local and PWA code</li>
                             <li>Further implementation of Service Worker mode in UWP app (PC, not mobile)</li>
                             <li>Fix display of masonry tiles in JQuery mode with latest ZIMs</li>