diff --git a/mozilla/calendar/base/content/calendar-recurrence-dialog.js b/mozilla/calendar/base/content/calendar-recurrence-dialog.js
index ce6716a4f9f..4cc91a90cf2 100644
--- a/mozilla/calendar/base/content/calendar-recurrence-dialog.js
+++ b/mozilla/calendar/base/content/calendar-recurrence-dialog.js
@@ -131,7 +131,7 @@ function loadDialog()
     if (rules.length > 0) {
         // we only handle 1 rule currently
         var rule = rules[0];
-        if (rule instanceof calIRecurrenceRule) {
+        if (rule instanceof Ci.calIRecurrenceRule) {
 
             switch(rule.type) {
             case "DAILY":
@@ -232,7 +232,7 @@ function saveDialog()
         recurrenceInfo.item = window.calendarEvent;
     }
 
-    var recRule = new calRecurrenceRule();
+    var recRule = createRecurrenceRule();
     switch (deckNumber) {
     case 0:
         recRule.type = "DAILY";
diff --git a/mozilla/calendar/base/src/calUtils.js b/mozilla/calendar/base/src/calUtils.js
index 71463e60db2..90525968dd6 100644
--- a/mozilla/calendar/base/src/calUtils.js
+++ b/mozilla/calendar/base/src/calUtils.js
@@ -65,6 +65,12 @@ function createRecurrenceInfo() {
            createInstance(Ci.calIRecurrenceInfo);
 }
 
+/* Returns a clean new calIRecurrenceRule */
+function createRecurrenceRule() {
+    return Cc["@mozilla.org/calendar/recurrence-rule;1"].
+           createInstance(Ci.calIRecurrenceRule);
+}
+
 /* Returns a clean new calIAttendee */
 function createAttendee() {
     return Cc["@mozilla.org/calendar/attendee;1"].