diff --git a/modules/browser.js b/modules/browser.js
index 139f3148..9a540fd2 100644
--- a/modules/browser.js
+++ b/modules/browser.js
@@ -4189,7 +4189,7 @@ TreeStyleTabBrowser.prototype = {
 
 			if (aOptions.canExpandTree) {
 				if (aOptions.canCollapseTree &&
-					aSelf.getTreePref('autoExpand.intelligently'))
+					utils.getTreePref('autoExpand.intelligently'))
 					aSelf.collapseExpandTreesIntelligentlyFor(aTab);
 				else
 					aSelf.collapseExpandSubtree(aTab, false);