diff --git a/serial.inc b/serial.inc
index cb3dec2..cb28997 100644
--- a/serial.inc
+++ b/serial.inc
@@ -41,31 +41,33 @@ function _serial_drop_table($field, $instance) {
 }
 
 /**
- * Renames serial table(s) when a content type us renamed.
+ * Renames serial table(s) when a entity bundle us renamed.
  *
- * @param $old_type
- *   an old node type machine name
- * @param $new_type
- *   a new node type machine name
+ * @param $bundle_old
+ *   an old entity bundle machine name
+ * @param $bundle_new
+ *   a new entity bundle machine name
  */
-function _serial_rename_tables($old_type, $new_type) {
+function _serial_rename_tables($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 = db_select('field_config', 'f')
+    ->fields('f', array('field_name'));
   $table_joined_alias = $query->join(
       'field_config_instance', 'i',
-      '(f.field_name = i.field_name) AND ' .
-      '(f.type = :field_type) AND (i.bundle = :bundle_type)',
-      array(':field_type' => 'serial', ':bundle_type' => $new_type)
-  );
+      '(f.field_name = i.field_name)'
+    );
+  $query->condition('f.type', 'serial');
+  $query->condition('i.entity_type', $entity_type);
+  $query->condition('i.bundle', $bundle_new);
 
   // Add an access check and execute it.
   $result = $query->addTag('node_access')->execute();
 
   // Rename each affected table.
   foreach ($result as $record) {
-    $old_table = _serial_get_table_name($old_type, $record->field_name);
-    $new_table = _serial_get_table_name($new_type, $record->field_name);
+    $old_table = _serial_get_table_name($entity_type, $bundle_old, $record->field_name);
+    $new_table = _serial_get_table_name($entity_type, $bundle_new, $record->field_name);
     db_rename_table($old_table, $new_table);
   }
 }
@@ -81,22 +83,24 @@ function _serial_rename_tables($old_type, $new_type) {
  *   the name of the assistant table of the specified field instance.
  */
 function _serial_get_field_table_name($field, $instance) {
-  return _serial_get_table_name($instance['bundle'], $field['field_name']);
+  return _serial_get_table_name($instance['entity_type'], $instance['bundle'], $field['field_name']);
 }
 
 /**
  * Gets the name of the assistant table for a specific field.
  *
+ * @param $entity_type
+ *   type of entity (e.g. node)
  * @param $bundle
- *   the name of the entity type that contains the field
+ *   the name of the entity type that contains the field (e.g. content type)
  * @param $field_name
  *   the name of the field
  * @return
  *   the name of the assistant table of the specified field.
  */
-function _serial_get_table_name($bundle, $field_name) {
+function _serial_get_table_name($entity_type, $bundle, $field_name) {
   return db_escape_table( // be on the safe side
-    'serial_' . $bundle . '_' . $field_name);
+    'serial_' . $entity_type . '_' . $bundle . '_' . $field_name);
 }
 
 /**
@@ -129,10 +133,10 @@ function _serial_get_table_schema() {
 }
 
 /**
- * Generates a unique serial value (unique per node type).
+ * Generates a unique serial value (unique per entity bundle).
  *
- * @param $nid
- *   id of the node for which to generate a serial value
+ * @param $entity_type
+ *   type of entity (e.g. node)
  * @param $bundle
  *   a containing bundle (e.g. content type)
  * @param $field_name
@@ -142,10 +146,10 @@ function _serial_get_table_schema() {
  * @return
  *   the unique serial value number.
  */
-function _serial_generate_value($bundle, $field_name, $delete = TRUE) {
+function _serial_generate_value($entity_type, $bundle, $field_name, $delete = TRUE) {
 
   // Get the name of the relevant table.
-  $table = _serial_get_table_name($bundle, $field_name);
+  $table = _serial_get_table_name($entity_type, $bundle, $field_name);
 
   // Insert a temporary record to get a new unique serial value.
   $uniqid = uniqid('', TRUE);
@@ -170,48 +174,67 @@ function _serial_generate_value($bundle, $field_name, $delete = TRUE) {
 }
 
 /**
- * Initializes the value of a new serial field in existing nodes.
+ * Initializes the value of a new serial field in existing entities.
  *
+ * @param $entity_type
+ *   type of entity (e.g. node)
  * @param $bundle
  *   a containing bundle (e.g. content type)
  * @param $field_name
  *   the field name
  * @return
- *   the number of existing nodes that have been initialized.
+ *   the number of existing entities that have been initialized.
  */
-function _serial_init_old_nodes($bundle, $field_name) {
-  // Retrieve all the node ids of that type:
-  $query = "SELECT nid FROM {node} WHERE type = :type ORDER BY nid";
-    // TODO: Currently works only for nodes - should support comments and users.
-  $result = db_query($query, array('type' => $bundle));
+function _serial_init_old_entities($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 .= "ORDER BY $id_key";
 
-  // Allocate a serial number for every old node:
+  // 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:
   $count = 0;
-  foreach ($result as $node) {
-    $nid = $node->nid;
-    $node = node_load($nid);
-    $sid = _serial_generate_value($bundle, $field_name, FALSE);
-    $node->{$field_name} = array('und' => array(array('value' => $sid)));
-    node_save($node);
-    $count++;
+  foreach ($results as $result) {
+    $id = $result->{$id_key};
+    if ($id > 0) {
+      // Check for valid id. Prevent anonymous user from being updated.
+      $entity = entity_load_single($entity_type, $id);
+      $sid = _serial_generate_value($entity_type, $bundle, $field_name, FALSE);
+      $entity->{$field_name} = array('und' => array(array('value' => $sid)));
+      entity_save($entity_type, $entity);
+      $count++;
+    }
   }
 
-  // Return the number of existing nodes that have been initialized:
+  // Return the number of existing entities that have been initialized:
   return $count;
 }
 
 /**
  * Retrieves all the managed serial fields.
  *
- * @return result set containing pairs of (node type name, field name).
+ * @return result set containing of (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');
-  $query->fields('i', array('bundle', 'field_name'))
+  $query->fields('i', array('entity_type', 'bundle', 'field_name'))
         ->condition('f.type', 'serial', '=')
         ->condition('i.deleted', 0, '=');
   $result = $query->execute();
   return $result->fetchAll();
 }
-
diff --git a/serial.info b/serial.info
index 56dfddd..322b7db 100644
--- a/serial.info
+++ b/serial.info
@@ -2,6 +2,7 @@ name = Serial
 description = Defines atomic auto increment (serial) field type.
 package = Fields
 core = 7.x
+dependencies[] = entity
 dependencies[] = field
 files[] = serial.module
 
diff --git a/serial.install b/serial.install
index 18e72bf..019eb00 100644
--- a/serial.install
+++ b/serial.install
@@ -48,7 +48,7 @@ function serial_schema() {
   $schema = array();
   $result = _serial_get_all_fields();
   foreach ($result as $field) {
-    $table = _serial_get_table_name($field->bundle, $field->field_name);
+    $table = _serial_get_table_name($field->entity_type, $field->bundle, $field->field_name);
     $schema[$table] = $table_schema;
   }
 
@@ -71,7 +71,7 @@ function serial_update_7130() {
   $result = _serial_get_all_fields();
   foreach ($result as $field) {
     // Empty the table.
-    $table = _serial_get_table_name($field->bundle, $field->field_name);
+    $table = _serial_get_table_name($field->entity_type, $field->bundle, $field->field_name);
     db_delete($table)->execute();
 
     // Drop nid field and key
@@ -84,3 +84,15 @@ function serial_update_7130() {
   }
 }
 
+/**
+ * Add 'node_' to all serial tables.
+ *
+ * Change 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_without_serial = preg_replace('/^serial_/', '', $tablename);
+    db_rename_table($tablename, 'serial_node_' . $tablename_without_serial);
+  }
+}
diff --git a/serial.module b/serial.module
index 688bb10..e79427d 100644
--- a/serial.module
+++ b/serial.module
@@ -34,10 +34,10 @@ function serial_field_create_instance($instance) {
     _serial_create_table($field, $instance);
 
     // Set serial values for old objects
-    $old_count = _serial_init_old_nodes($instance['bundle'], $field['field_name']);
+    $old_count = _serial_init_old_entities($instance['entity_type'], $instance['bundle'], $field['field_name']);
     if ($old_count) {
       drupal_set_message(
-        t('Serial values have been automatically set for %count existing nodes.',
+        t('Serial values have been automatically set for %count existing entities.',
           array('%count' => $old_count))
       );
     }
@@ -68,10 +68,6 @@ function serial_form_alter(&$form, $form_state, $form_id) {
       t('Serial field %field has been created.',
         array('%field' => $field_name))
     );
-
-    // Go back to Managed Fields:
-    $type = $form['#bundle'];
-    drupal_goto("admin/structure/types/manage/$type/fields");
   }
 }
 
@@ -81,7 +77,7 @@ function serial_form_alter(&$form, $form_state, $form_id) {
 function serial_field_presave($entity_type, $entity, $field, $instance, $langcode, &$items) {
   module_load_include('inc', 'serial');
   if (empty($items)) {
-    $sid = _serial_generate_value($instance['bundle'], $field['field_name']);
+    $sid = _serial_generate_value($entity_type, $instance['bundle'], $field['field_name']);
     $items = array(array('value' => $sid));
   }
 }
@@ -106,13 +102,13 @@ function serial_node_presave($node) {
 }
 
 /**
- * Implements hook_node_type_update().
+ * Implements hook_field_attach_rename_bundle().
  */
-function serial_node_type_update($info) {
-  // Handle content type rename:
-  if (isset($info->old_type) && ($info->old_type != $info->type)) {
+function serial_field_attach_rename_bundle($entity_type, $bundle_old, $bundle_new) {
+  // Update the extra weights variable with new information.
+  if ($bundle_old !== $bundle_new) {
     module_load_include('inc', 'serial');
-    _serial_rename_tables($info->old_type, $info->type);
+    _serial_rename_tables($entity_type, $bundle_old, $bundle_new);
   }
 }
 
@@ -231,4 +227,3 @@ function serial_field_widget(&$form, &$form_state, $field, $instance, $items, $d
     )
   );
 }
-