diff --git a/field_validation.module b/field_validation.module
index c3c8c6e..86f4419 100644
--- a/field_validation.module
+++ b/field_validation.module
@@ -54,7 +54,7 @@ function field_validation_menu() {
             'type' => MENU_LOCAL_TASK,
             'file' => 'field_validation.admin.inc',
           ) + $access;
-					
+
           $items[$path.'/fields/%field_ui_menu/validation/add'] = array(
             'load arguments' => array($entity_type, $bundle_arg, $bundle_pos, '%map'),
             'title' => 'Add validation',
@@ -63,7 +63,7 @@ function field_validation_menu() {
             'type' => MENU_CALLBACK,
             'file' => 'field_validation.admin.inc',
           ) + $access;
-					
+
 					$items["$path/fields/%field_ui_menu/validation/edit"] = array(
             'load arguments' => array($entity_type, $bundle_arg, $bundle_pos, '%map'),
             'title' => 'Edit rule',
@@ -72,7 +72,7 @@ function field_validation_menu() {
             'type' => MENU_CALLBACK,
             'file' => 'field_validation.admin.inc',
           ) + $access;
-					
+
 					$items["$path/fields/%field_ui_menu/validation/delete"] = array(
             'load arguments' => array($entity_type, $bundle_arg, $bundle_pos, '%map'),
             'title' => 'Delete rule',
@@ -85,7 +85,7 @@ function field_validation_menu() {
       }
     }
   }
-	
+
   return $items;
 }
 
@@ -135,7 +135,7 @@ function field_validation_field_attach_validate($entity_type, $entity, &$errors)
 				}
 
 			}
-			
+
 		}
   }
 }
@@ -210,22 +210,27 @@ function field_validation_rule_save($values) {
  */
 function field_validation_form_field_ui_field_overview_form_alter(&$form, &$form_state) {
   $entity_type = $form['#entity_type'];
-	$bundle = $form['#bundle'];
+  $bundle = $form['#bundle'];
 
   $bundle = field_extract_bundle($entity_type, $bundle);
-	$admin_path = _field_ui_bundle_admin_path($entity_type, $bundle);
-	
+  $admin_path = _field_ui_bundle_admin_path($entity_type, $bundle);
+
   $table = &$form['fields'];
-	$table['#header'][6]['colspan'] = 3;
-	$instances = field_info_instances($entity_type, $bundle);
-	foreach ($instances as $name => $instance) {
-	  $field = field_info_field($instance['field_name']);
-		$admin_field_path = $admin_path . '/fields/' . $instance['field_name'];
-		$table[$name]['validation'] = array(
-		  '#type' => 'link',
-			'#title' => t('validate'),
-			'#href' => $admin_field_path . '/validation',
-			'#options' => array('attributes' => array('title' => t('Manage validation rules.'))),
-		);
-	}
+  $table['#header'][6]['colspan'] = 3;
+  $instances = field_info_instances($entity_type, $bundle);
+  foreach ($instances as $name => $instance) {
+    if (!isset($instance['locked']) || $instance['locked'] == false) {
+      $field = field_info_field($instance['field_name']);
+      $admin_field_path = $admin_path . '/fields/' . $instance['field_name'];
+      $table[$name]['validation'] = array(
+        '#type' => 'link',
+        '#title' => t('validate'),
+        '#href' => $admin_field_path . '/validation',
+        '#options' => array('attributes' => array('title' => t('Manage validation rules.'))),
+      );
+    }
+    else {
+      $table[$name]['validation'] = array('#markup' => '');
+    }
+  }
 }
\ No newline at end of file