--- a/suite/common/places/nsPlacesAutoComplete.js
+++ b/suite/common/places/nsPlacesAutoComplete.js
@@ -181,17 +181,17 @@ function fixupSearchText(aURIString)
   return gTextURIService.unEscapeURIForUI("UTF-8", uri);
 }
 
 /**
  * safePrefGetter get the pref with typo safety.
  * This will return the default value provided if no pref is set.
  *
  * @param aPrefBranch
- *        The nsIPrefBranch2 containing the required preference
+ *        The nsIPrefBranch containing the required preference
  * @param aName
  *        A preference name
  * @param aDefault
  *        The preference's default value
  * @return the preference value or provided default
  */
 
 function safePrefGetter(aPrefBranch, aName, aDefault) {
@@ -871,18 +871,17 @@ nsPlacesAutoComplete.prototype = {
     // Validate matchBehavior; default to MATCH_BOUNDARY_ANYWHERE.
     if (this._matchBehavior != MATCH_ANYWHERE &&
         this._matchBehavior != MATCH_BOUNDARY &&
         this._matchBehavior != MATCH_BEGINNING) {
       this._matchBehavior = MATCH_BOUNDARY_ANYWHERE;
     }
     // register observer
     if (aRegisterObserver) {
-      let pb = this._prefs.QueryInterface(Ci.nsIPrefBranch2);
-      pb.addObserver("", this, false);
+      this._prefs.addObserver("", this, false);
     }
   },
 
   /**
    * Given an array of tokens, this function determines which query should be
    * ran.  It also removes any special search tokens.
    *
    * @param aTokens