diff --git a/entityreference.install b/entityreference.install
index 4e248ef..087e832 100644
--- a/entityreference.install
+++ b/entityreference.install
@@ -20,7 +20,7 @@ function entityreference_field_schema($field) {
         'target_id' => array(
           'description' => 'The id of the target entity.',
           'type' => 'int',
-          'unsigned' => TRUE,
+          'unsigned' => FALSE,//@TODO hacking by zkday.
           'not null' => TRUE,
         ),
       ),
@@ -161,4 +161,39 @@ function entityreference_update_7002() {
       'not null' => TRUE,
     ));
   }
-}
\ No newline at end of file
+}
+
+/**
+ * Make the target_id is unsigned is FALSE.
+ */
+function entityreference_update_7003() {
+  if (!module_exists('field_sql_storage')) {
+    return;
+  }
+  
+  foreach (field_info_fields() as $field_name => $field) {
+    if ($field['type'] != 'entityreference') {
+      continue;
+    }
+    if ($field['storage']['type'] !== 'field_sql_storage') {
+     // Field doesn't use SQL storage, we cannot modify the schema.
+     continue;
+    }
+    
+    $table_name = _field_sql_storage_tablename($field);
+    $revision_name = _field_sql_storage_revision_tablename($field);
+    
+    db_change_field($table_name, $field_name . '_target_id', $field_name . '_target_id', array(
+      'description' => 'The id of the target entity.',
+      'type' => 'int',
+      'unsigned' => FALSE,
+      'not null' => TRUE,
+    ));
+    db_change_field($revision_name, $field_name . '_target_id', $field_name . '_target_id', array(
+      'description' => 'The id of the target entity.',
+      'type' => 'int',
+      'unsigned' => FALSE,
+      'not null' => TRUE,
+    ));
+  }
+}
diff --git a/entityreference.module b/entityreference.module
index 5f03c5b..5adb269 100644
--- a/entityreference.module
+++ b/entityreference.module
@@ -188,6 +188,8 @@ function entityreference_get_selection_handler($field, $instance = NULL, $entity
   $handler = $field['settings']['handler'];
   $class = ctools_plugin_load_class('entityreference', 'selection', $handler, 'class');
 
+/////z-debug: dsm($class, 'class');
+
   if (class_exists($class)) {
     return call_user_func(array($class, 'getInstance'), $field, $instance, $entity_type, $entity);
   }