diff --git a/CategoryTree.php b/CategoryTree.php
index 0946d103..0f1d6274 100644
--- a/CategoryTree.php
+++ b/CategoryTree.php
@@ -49,8 +49,12 @@ $wgCategoryTreeUnifiedView = true;
 $wgCategoryTreeOmitNamespace = false;
 $wgCategoryTreeMaxDepth = array(CT_MODE_PAGES => 1, CT_MODE_ALL => 1, CT_MODE_CATEGORIES => 2);
 $wgCategoryTreeExtPath = '/extensions/CategoryTree';
-$wgCategoryTreeDefaultMode = CT_MODE_CATEGORIES;
-$wgCategoryTreeCategoryPageMode = CT_MODE_CATEGORIES;
+if ( ! isset( $wgCategoryTreeDefaultMode ) ) {
+	$wgCategoryTreeDefaultMode = CT_MODE_CATEGORIES;
+}
+if ( ! isset( $wgCategoryTreeCategoryPageMode ) ) {
+	$wgCategoryTreeCategoryPageMode = CT_MODE_CATEGORIES;
+}
 $wgCategoryTreeVersion = '1';
 
 /**