diff --git a/static/viewer.html b/static/viewer.html
index ea50fecfe..ca059e684 100644
--- a/static/viewer.html
+++ b/static/viewer.html
@@ -35,9 +35,20 @@
       }
 
       const cf = document.getElementById('content_iframe');
-      cf.src = userUrl2IframeUrl(window.location.hash.slice(1));
       cf.height = window.visualViewport.height - cf.offsetTop - 4;
 
+      function handle_location_hash_change() {
+        const hash = window.location.hash;
+        const iframeContentUrl = userUrl2IframeUrl(hash.slice(1));
+        console.log("handle_location_hash_change: " + hash);
+        if ( iframeContentUrl != cf.contentWindow.location.pathname ) {
+          cf.src = iframeContentUrl;
+        }
+      }
+
+      window.onhashchange = handle_location_hash_change;
+      handle_location_hash_change();
+
       function handle_content_url_change() {
         document.title = cf.contentDocument.title;
         const iframeContentUrl = cf.contentWindow.location.pathname;