--- a/browser/base/content/tabbrowser.xml
+++ b/browser/base/content/tabbrowser.xml
@@ -5514,20 +5514,23 @@
           let modifiedAttrs = [];
           if (tab.hasAttribute("soundplaying-scheduledremoval")) {
             tab.removeAttribute("soundplaying-scheduledremoval");
             modifiedAttrs.push("soundplaying-scheduledremoval");
           }
 
           if (!tab.hasAttribute("soundplaying")) {
             tab.setAttribute("soundplaying", true);
+            modifiedAttrs.push("soundplaying");
+          }
+
+          if (modifiedAttrs.length) {
             // Flush style so that the opacity takes effect immediately, in
             // case the media is stopped before the style flushes naturally.
             getComputedStyle(tab).opacity;
-            modifiedAttrs.push("soundplaying");
           }
 
           this._tabAttrModified(tab, modifiedAttrs);
         ]]>
       </handler>
       <handler event="DOMAudioPlaybackStopped">
         <![CDATA[
           var tab = getTabFromAudioEvent(event)