diff --git a/lib/Doctrine/Connection.php b/lib/Doctrine/Connection.php
index 842071ab1..fc1f5a11b 100644
--- a/lib/Doctrine/Connection.php
+++ b/lib/Doctrine/Connection.php
@@ -544,7 +544,7 @@ abstract class Doctrine_Connection extends Doctrine_Configurable implements Coun
         foreach ($fields as $fieldName => $value) {
             if ($value instanceof Doctrine_Expression) {
                 $set[] = $table->getColumnName($fieldName) . ' = ' . $value->getSql();
-                unset($values[$name]);
+                unset($fields[$name]);
             } else {
                 $set[] = $table->getColumnName($fieldName) . ' = ?';
             }