diff --git a/CRM/ConstituentsOnly/BAO/Query.php b/CRM/ConstituentsOnly/BAO/Query.php
index d23c644..b9e033a 100644
--- a/CRM/ConstituentsOnly/BAO/Query.php
+++ b/CRM/ConstituentsOnly/BAO/Query.php
@@ -18,14 +18,12 @@ class CRM_ConstituentsOnly_BAO_Query extends CRM_Contact_BAO_Query_Interface {
    * @access public
    */
   public function where(&$query) {
-    $grouping = 0;
-    $statement = "NOT (contact_a.do_not_trade <=> 1)";
-    $query->_where[$grouping][] = $statement;
+    if (CRM_Utils_Array::value('civicrm_contact', $query->_tables)) {
+      $query->_where[0][] = "( contact_a.do_not_trade IS NULL OR contact_a.do_not_trade = 0)";
+    }
   }
 
   public function from($name, $mode, $side) {
-    $from = NULL;
-    return $from;
   }
 
   public function setTableDependency(&$tables) {