diff --git a/modules/browser.js b/modules/browser.js
index 92ba45b6..ec61852a 100644
--- a/modules/browser.js
+++ b/modules/browser.js
@@ -4497,7 +4497,10 @@ TreeStyleTabBrowser.prototype = inherit(TreeStyleTabWindow.prototype, {
 					aChild.toggleMuteAudio();
 			}, this);
 		}
-		return this.getTabValue(aTab, this.kREALLY_SOUND_PLAYING) != 'true';
+		return (
+			this.getTabValue(aTab, this.kREALLY_SOUND_PLAYING) != 'true' ||
+			aTab.getAttribute('muted') == 'true' // allow to unmute tab always, even if the sound is not played
+		);
 	},
  
 	correctChildTabsOrderWithDelay : function TSTBrowser_correctChildTabsOrderWithDelay(aTab)