diff --git a/CHANGES b/CHANGES
index f83a075..a1ee59d 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,6 +1,7 @@
 Galene 0.8 (unreleased)
 
   * Change default video codec to VP9.
+  * Disable simulcast on Firefox by default.
 
 9 July 2023: Galene 0.7.2
 
diff --git a/static/galene.js b/static/galene.js
index 49d4379..7e6d4d2 100644
--- a/static/galene.js
+++ b/static/galene.js
@@ -280,6 +280,11 @@ function isSafari() {
     return ua.indexOf('safari') >= 0 && ua.indexOf('chrome') < 0;
 }
 
+function isFirefox() {
+    let ua = navigator.userAgent.toLowerCase();
+    return ua.indexOf('firefox') >= 0;
+}
+
 /** @type {MediaStream} */
 let safariStream = null;
 
@@ -3918,6 +3923,10 @@ async function start() {
         );
     }
 
+    // Disable simulcast on Firefox by default, it's buggy.
+    if(isFirefox())
+        getSelectElement('simulcastselect').value = 'off';
+
     let parms = new URLSearchParams(window.location.search);
     if(window.location.search)
         window.history.replaceState(null, '', window.location.pathname);