diff --git a/entity_translation.module b/entity_translation.module
index 947caff..20dde72 100644
--- a/entity_translation.module
+++ b/entity_translation.module
@@ -2078,3 +2078,60 @@ function entity_translation_entity_save($entity_type, $entity) {
     field_attach_update($entity_type, $entity);
   }
 }
+
+/**
+ * Migrate existing field content from language "undefined" to entity language.
+ *
+ * This is an API function that can be called from a hook_update_N()
+ * implementation as follows:
+ * @code
+ * function mymodule_update_N(&$sandbox) {
+ *   return entity_translation_migrate_field_content_update($sandbox);
+ * }
+ * @endcode
+ *
+ * Using this API function is necessary when fields are made translatable via
+ * some deployment method (like using the features module) as the regular batch
+ * migration is not triggered in this case.
+ */
+function entity_translation_migrate_field_content_update(&$sandbox) {
+  // Number of entities to be processed for each step.
+  $messages = array();
+  if (!isset($sandbox['fields'])) {
+    // Initialize the array of field to process.
+    $sandbox['fields'] = array_filter(field_info_fields(), function($field_info) {return $field_info['translatable'];});
+    foreach (array_keys($sandbox['fields']) as $field_name) {
+      $sandbox['fields'][$field_name]['context'] = array('sandbox' => array(), 'finished' => 0);
+    }
+  }
+  // Search for an unfinished field.
+  $field_names = array_keys($sandbox['fields']);
+  $field_name = &reset($field_names);
+  while ($field_name && $sandbox['fields'][$field_name]['context']['finished'] >= 1) {
+    $field_name = &next($field_names);
+  }
+  if ($field_name) {
+    // Process the field.
+    module_load_include('inc', 'entity_translation', 'entity_translation.admin');
+    entity_translation_translatable_batch(TRUE, $sandbox['fields'][$field_name]['field_name'], TRUE, $sandbox['fields'][$field_name]['context']);
+    $sandbox['#finished'] = array_reduce($sandbox['fields'], function($carry, $item) {
+        return $carry + $item['context']['finished'];
+      }, 0) / count($sandbox['fields']);
+    $message_args = array(
+      '@field_name' => $sandbox['fields'][$field_name]['field_name'],
+      '@progress' => (number_format($sandbox['#finished'] * 100)),
+      '@field_progress' => (number_format($sandbox['fields'][$field_name]['context']['finished'] * 100)),
+    );
+    if ($sandbox['fields'][$field_name]['context']['finished'] >= 1) {
+      $messages[] = format_string('@progress - Done with @field_name.', $message_args);
+    }
+    else {
+      $messages[] = format_string('@progress - Processing @field_name (@field_progress)... ', $message_args);
+    }
+  }
+  else {
+    // No more field to process, we are done.
+    $sandbox['#finished'] = 1;
+  }
+  return implode("\n", $messages);
+}