diff --git a/calendar/lightning/content/messenger-overlay-sidebar.js b/calendar/lightning/content/messenger-overlay-sidebar.js
index 0f1de2364c..83d31d7139 100644
--- a/calendar/lightning/content/messenger-overlay-sidebar.js
+++ b/calendar/lightning/content/messenger-overlay-sidebar.js
@@ -66,6 +66,14 @@ var calendarTabType = {
       },
       showTab: function(aTab) {
         ltnSwitch2Calendar();
+      },
+      closeTab: function(aTab) {
+        if (gCurrentMode == "calendar") {
+          // Only revert menu hacks if closing the active tab, otherwise we
+          // would switch to mail mode even if in task mode and closing the
+          // calendar tab.
+          ltnSwitch2Mail();
+        }
       }
     },
     tasks: {
@@ -77,6 +85,14 @@ var calendarTabType = {
       },
       showTab: function(aTab) {
         ltnSwitch2Task();
+      },
+      closeTab: function(aTab) {
+        if (gCurrentMode == "task") {
+          // Only revert menu hacks if closing the active tab, otherwise we
+          // would switch to mail mode even if in calendar mode and closing the
+          // tasks tab.
+          ltnSwitch2Mail();
+        }
       }
     },
   },
@@ -87,9 +103,6 @@ var calendarTabType = {
   saveTabState: function(aTab) {
     ltnSwitch2Mail();
   },
-  closeTab: function(aTab) {
-    ltnSwitch2Mail();
-  },
 };
 window.addEventListener("load", function(e) { 
   document.getElementById('tabmail').registerTabType(calendarTabType); }, false);