diff -u b/serial.inc b/serial.inc
--- b/serial.inc
+++ b/serial.inc
@@ -43,21 +43,20 @@
 /**
  * Renames serial table(s) when a entity bundle us renamed.
  *
- * @param $bundle_old
- *   An old entity bundle machine name
- * @param $bundle_new
- *   A new entity bundle machine name
+ * @param string $entity_type
+ *   Type of entity.
+ * @param string $bundle_old
+ *   An old entity bundle machine name.
+ * @param string $bundle_new
+ *   A new entity bundle machine name.
  */
 function _serial_rename_tables($entity_type, $bundle_old, $bundle_new) {
   // Build the query to find all affected tables.
   $query = db_select('field_config', 'f')
     ->fields('f', array('field_name'));
 
-  $query->join(
-    'field_config_instance',
-    'i',
-    "(f.field_name = i.field_name)"
-  );
+  $query->join('field_config_instance', 'i', '(f.field_name = i.field_name)');
+
   $query->condition('f.type', 'serial');
   $query->condition('i.entity_type', $entity_type);
   $query->condition('i.bundle', $bundle_new);
@@ -89,7 +88,7 @@
 /**
  * Gets the name of the assistant table for a specific field.
  *
- * @param $entity_type
+ * @param string $entity_type
  *   Type of entity (e.g. node)
  * @param string $bundle
  *   The name of the entity type that contains the field (e.g. content type)
@@ -100,7 +99,7 @@
  *   The name of the assistant table of the specified field.
  */
 function _serial_get_table_name($entity_type, $bundle, $field_name) {
-  return db_escape_table('serial_' . $entity_type . '_' . $bundle . '_' . $field_name);
+  return db_escape_table("serial_{$entity_type}_{$bundle}_{$field_name}");
 }
 
 /**
@@ -114,16 +113,17 @@
     'fields' => array(
       'sid' => array(
         'type' => 'serial',
-        'unsigned' => TRUE,
         'not null' => TRUE,
+        'unsigned' => TRUE,
         'description' => 'The atomic serial field.',
       ),
       'uniqid' => array(
-        'description' => 'Unique temporary allocation Id.',
         'type' => 'varchar',
         'length' => 23,
+        'default' => '',
         'not null' => TRUE,
-        'default' => ''),
+        'description' => 'Unique temporary allocation Id.',
+      ),
     ),
     'primary key' => array('sid'),
     'unique keys' => array(
@@ -135,7 +135,7 @@
 /**
  * Generates a unique serial value (unique per entity bundle).
  *
- * @param $entity_type
+ * @param string $entity_type
  *   Type of entity (e.g. node)
  * @param string $bundle
  *   Containing bundle (e.g. content type).
@@ -150,7 +150,6 @@
 function _serial_generate_value($entity_type, $bundle, $field_name, $delete = TRUE) {
   // Get the name of the relevant table.
   $table = _serial_get_table_name($entity_type, $bundle, $field_name);
-
   // Insert a temporary record to get a new unique serial value.
   $uniqid = uniqid('', TRUE);
   $sid = db_insert($table)
@@ -174,9 +173,7 @@
 /**
  * Initializes the value of a new serial field in existing entities.
  *
- * @todo Currently works only for nodes - should support comments and users.
- *
- * @param $entity_type
+ * @param string $entity_type
  *   Type of entity (e.g. node)
  * @param string $bundle
  *   Containing bundle (e.g. content type).
@@ -187,33 +184,23 @@
  *   Number of existing entities that have been initialized.
  */
 function _serial_init_old_entities($entity_type, $bundle, $field_name) {
-  // Prepare meta data.
-  $entity_info = entity_get_info($entity_type);
-  $base_table = $entity_info['base table'];
-  $bundle_key = $entity_info['entity keys']['bundle'];
-  $id_key = $entity_info['entity keys']['id'];
-
-  // @todo - What if $base_table or $id_key is empty?
-
-  // Build the query.
-  $query = "SELECT $id_key FROM {$base_table} ";
-  if (!empty($bundle_key)) {
-    // Some entity types (e.g. user) do not have bundle.
-    $query .= "WHERE $bundle_key = :type ";
+  $query = new EntityFieldQuery();
+  $query->entityCondition('entity_type', $entity_type)
+    ->fieldCondition($field_name);
+
+  // The "comment" entity type does not support bundle conditions.
+  // @see https://api.drupal.org/api/drupal/includes!entity.inc/function/EntityFieldQuery%3A%3AentityCondition/7
+  if ('comment' !== $entity_type) {
+    $query->entityCondition('bundle', $bundle);
   }
-  $query .= "ORDER BY $id_key";
 
-  // Execute the query.
-  // @todo - Which is better: EntityFieldQuery or db_query?
-  $results = db_query($query, array('type' => $bundle));
-
-  // Allocate a serial number for every old entity:
-  $count = 0;
-  foreach ($results as $result) {
-    $id = $result->{$id_key};
-    if ($id > 0) {
-      // Check for valid id. Prevent anonymous user from being updated.
-      $entity = entity_load($entity_type, array($id));
+  $results = $query->execute();
+
+  if (!empty($results[$entity_type])) {
+    $entity_info = entity_get_info($entity_type);
+
+    foreach ($results[$entity_type] as $entity) {
+      $entity = entity_load_unchanged($entity_type, $entity->{$entity_info['entity keys']['id']});
       $entity->{$field_name} = array(
         LANGUAGE_NONE => array(
           array(
@@ -221,26 +208,28 @@
           ),
         ),
       );
-      entity_save($entity_type, $entity);
-      $count++;
+
+      field_attach_insert($entity_type, $entity);
     }
+
+    return count($results[$entity_type]);
   }
 
-  // Return the number of existing entities that have been initialized.
-  return $count;
+  return 0;
 }
 
 /**
  * Retrieves all the managed serial fields.
  *
- * @return array
+ * @return string[]
  *   Result set containing entity type, entity bundle, field name.
  */
 function _serial_get_all_fields() {
   $query = db_select('field_config', 'f');
   $query->join('field_config_instance', 'i', 'i.field_name = f.field_name');
 
-  return $query->fields('i', array('entity_type', 'bundle', 'field_name'))
+  return $query
+    ->fields('i', array('entity_type', 'bundle', 'field_name'))
     ->condition('f.type', 'serial')
     ->condition('i.deleted', 0)
     ->execute()
diff -u b/serial.install b/serial.install
--- b/serial.install
+++ b/serial.install
@@ -72,13 +72,14 @@
 
 /**
- * Add 'node_' to all serial tables.
+ * Add 'node_' to all existing serial tables.
  *
- * Change from serial_{content type}_{field name} to serial_node_{content type}_{field name}
+ * Change name:
+ *   from: serial_{content_type}_{field_name}
+ *   to: serial_node_{content_type}_{field_name}
  */
 function serial_update_7131() {
   // All old serial tables are of 'node' entity type.
-  foreach (db_find_tables('serial_%') as $tablename) {
-    $tablename_add_node = preg_replace('/^serial_/', 'serial_node_', $tablename);
-    db_rename_table($tablename, $tablename_add_node);
+  foreach (db_find_tables('serial_%') as $table) {
+    db_rename_table($table, preg_replace('/^serial_/', 'serial_node_', $table));
   }
 }
diff -u b/serial.module b/serial.module
--- b/serial.module
+++ b/serial.module
@@ -24,7 +24,7 @@
 /**
  * Implements hook_field_create_instance().
  */
-function serial_field_create_instance($instance) {
+function serial_field_create_instance(array $instance) {
   $field = field_read_field($instance['field_name']);
 
   if ('serial' == $field['type']) {
@@ -46,7 +46,7 @@
 /**
  * Implements hook_field_delete_instance().
  */
-function serial_field_delete_instance($instance) {
+function serial_field_delete_instance(array $instance) {
   $field = field_read_field($instance['field_name']);
 
   if ('serial' == $field['type']) {
@@ -59,7 +59,7 @@
 /**
  * Implements hook_form_alter().
  */
-function serial_form_alter(&$form, $form_state, $form_id) {
+function serial_form_alter(array &$form, array &$form_state, $form_id) {
   if ('field_ui_field_settings_form' == $form_id && 'serial' == $form['field']['type']['#value']) {
     drupal_set_message(t('Serial field %field has been created.', array(
       '%field' => $form['field']['field_name']['#value'],
@@ -72,11 +72,15 @@
 /**
  * Implements hook_field_presave().
  */
-function serial_field_presave($entity_type, $entity, $field, $instance, $langcode, &$items) {
+function serial_field_presave($entity_type, $entity, array $field, array $instance, $langcode, array &$items) {
   if (empty($items)) {
     module_load_include('inc', 'serial');
 
-    $items = array(array('value' => _serial_generate_value($entity_type, $instance['bundle'], $field['field_name'])));
+    $items = array(
+      array(
+        'value' => _serial_generate_value($entity_type, $instance['bundle'], $field['field_name']),
+      ),
+    );
   }
 }
 
@@ -124,7 +128,7 @@
 /**
  * Implements hook_field_formatter_view().
  */
-function serial_field_formatter_view($entity_type, $entity, $field, $instance, $langcode, $items, $display) {
+function serial_field_formatter_view($entity_type, $entity, $field, $instance, $langcode, array $items, $display) {
   $element = array();
 
   // Define the field contents for the single default formatter.
@@ -156,7 +160,7 @@
 /**
  * Theme function for the default formatter.
  */
-function theme_serial_formatter_default($variables) {
+function theme_serial_formatter_default(array $variables) {
   return $variables['serial_id'];
 }
 
@@ -175,7 +179,7 @@
 /**
  * Implements hook_field_widget().
  */
-function serial_field_widget(&$form, &$form_state, $field, $instance, $items, $delta = 0) {
+function serial_field_widget(array &$form, array &$form_state, array $field, array $instance, array $items, $delta = 0) {
   return array(
     'value' => array(
       '#type' => 'hidden',
@@ -189,50 +193,42 @@
  *
  * Replace token for generic entity type.
  */
-function serial_tokens($type, $tokens, $data, $options) {
+function serial_tokens($type, array $tokens, array $data = array(), array $options = array()) {
   $replacements = array();
-  $sanitize = !empty($options['sanitize']);
-
   $entity_info = entity_get_info($type);
-  // Make sure type is entity type.
-  if (empty($entity_info)) {
+
+  if (empty($entity_info) || empty($data[$type])) {
     return $replacements;
   }
 
-  $entity_type = $type;
-  if (!empty($data[$entity_type])) {
-    // Generic entity.
-    $entity = $data[$entity_type];
-    foreach ($tokens as $name => $original) {
-      // Convert token to field name.
-      $field_name = str_replace('-', '_', $name);
-      $field_info = field_info_field($field_name);
-      if ($field_info['type'] == 'serial') {
-        // Check if field is used in a pathauto pattern. If so, skip token replacement.
-        $pathauto_match = FALSE;
-        if (module_exists('pathauto')) {
-          $pattern = pathauto_pattern_load_by_entity($entity_type, $data[$entity_type]->type);
-          $path_items = explode('/', $pattern);
-          foreach ($path_items as $path_item) {
-            if (preg_match('/^\[(.*):field_(.*)\]$/', $path_item, $matches)) {
-              if ($field_name == 'field_' . $matches[2]) {
-                $pathauto_match = TRUE;
-                break;
-              }
-            }
-          }
-        }
-        if (!$pathauto_match) {
-          $items = field_get_items($entity_type, $entity, $field_name);
-          if (empty($items)) {
-            continue;
-          }
-          $item = reset($items);
-          $serial_value = $item['value'];
-          $replacements[$original] = $sanitize ? filter_xss($serial_value) : $serial_value;
-        }
+  $entity = $data[$type];
+  $pathauto = module_exists('pathauto');
+
+  foreach ($tokens as $name => $original) {
+    // Convert token to field name.
+    $field_name = str_replace('-', '_', $name);
+    $field_info = field_info_field($field_name);
+
+    if ('serial' === $field_info['type']) {
+      continue;
+    }
+
+    if ($pathauto) {
+      $pattern = pathauto_pattern_load_by_entity($type, $entity->{$entity_info['bundle keys']['bundle']});
+
+      if (strpos($pattern, "$type:$field_name") !== FALSE) {
+        continue;
       }
     }
+
+    /* @var array $items */
+    $items = field_get_items($type, $entity, $field_name);
+
+    if (FALSE !== $items) {
+      continue;
+    }
+
+    $replacements[$original] = $items[0]['value'];
   }
 
   return $replacements;
only in patch2:
unchanged:
--- a/serial.info
+++ b/serial.info
@@ -2,6 +2,5 @@ name = Serial
 description = Defines atomic auto increment (serial) field type.
 package = Fields
 core = 7.x
-dependencies[] = field
-files[] = serial.module
 
+dependencies[] = field