diff --git a/mozilla/calendar/base/content/calendar-month-view.xml b/mozilla/calendar/base/content/calendar-month-view.xml
index 8c544cf1364..91566697bdd 100644
--- a/mozilla/calendar/base/content/calendar-month-view.xml
+++ b/mozilla/calendar/base/content/calendar-month-view.xml
@@ -697,6 +697,11 @@
           }
       ]]></constructor>
 
+      <destructor><![CDATA[
+        if (this.mCalendar)
+            this.mCalendar.removeObserver(this.mObserver);
+      ]]></destructor>
+
       <!-- fields -->
 
       <field name="mCalendar">null</field>
diff --git a/mozilla/calendar/base/content/calendar-multiday-view.xml b/mozilla/calendar/base/content/calendar-multiday-view.xml
index 8b6ea30dd23..dff7bb877e7 100644
--- a/mozilla/calendar/base/content/calendar-multiday-view.xml
+++ b/mozilla/calendar/base/content/calendar-multiday-view.xml
@@ -1573,6 +1573,11 @@
         this.reorient();
       ]]></constructor>
 
+      <destructor><![CDATA[
+        if (this.mCalendar)
+            this.mCalendar.removeObserver(this.mObserver);
+      ]]></destructor>
+
       <method name="onResize">
         <parameter name="aRealSelf"/>
         <body><![CDATA[
diff --git a/mozilla/calendar/lightning/content/calendar-todo-list.xml b/mozilla/calendar/lightning/content/calendar-todo-list.xml
index f51d9297d06..545b4a0dbd3 100644
--- a/mozilla/calendar/lightning/content/calendar-todo-list.xml
+++ b/mozilla/calendar/lightning/content/calendar-todo-list.xml
@@ -46,6 +46,10 @@
     <binding id="calendar-todo-list" extends="chrome://global/content/bindings/richlistbox.xml#richlistbox"
              implements="calIObserver, calICompositeObserver, calIOperationListener">
         <implementation>
+        <destructor><![CDATA[
+          if (this.mCalendar)
+              this.mCalendar.removeObserver(this.mOperationListener);
+        ]]></destructor>
 
         <field name="mCalendar">null</field>
         <field name="mOperationListener"><![CDATA[
diff --git a/mozilla/calendar/lightning/content/messenger-overlay-sidebar.js b/mozilla/calendar/lightning/content/messenger-overlay-sidebar.js
index 09bda4cb7e1..d50cbf78896 100644
--- a/mozilla/calendar/lightning/content/messenger-overlay-sidebar.js
+++ b/mozilla/calendar/lightning/content/messenger-overlay-sidebar.js
@@ -295,6 +295,10 @@ function ltnFinish() {
     var pb2 = prefService.getBranch("");
     pb2 = pb2.QueryInterface(Components.interfaces.nsIPrefBranch2);
     pb2.removeObserver("calendar.", ltnPrefObserver);
+
+    getCompositeCalendar().removeObserver(agendaTreeView.calendarObserver);
+    getCompositeCalendar().removeObserver(ltnCompositeCalendarObserver);
+    getCalendarManager().removeObserver(ltnCalendarManagerObserver);
     return;
 }
 
diff --git a/mozilla/calendar/resources/content/calendarManagement.js b/mozilla/calendar/resources/content/calendarManagement.js
index 6b361b10083..cfda1eb4270 100644
--- a/mozilla/calendar/resources/content/calendarManagement.js
+++ b/mozilla/calendar/resources/content/calendarManagement.js
@@ -307,6 +307,7 @@ function finishCalendarManager() {
     var calendarList = document.getElementById("list-calendars-listbox");
     calendarList.removeEventListener("select", onCalendarListSelect, true);
 
+    getCalendarManager().removeObserver(calCalendarManagerObserver);
 }
 
 function getDefaultCalendar()
