diff --git entity.module entity.module
index c4df05f..78bc54e 100644
--- entity.module
+++ entity.module
@@ -595,7 +595,18 @@ function _entity_modules_get_default_types($modules) {
 
 /**
  * Defines schema fields required for exportable entities.
- * To be utilized by modules defining exportable entities.
+ *
+ * To be utilized by modules defining exportable entities. Since the upgrading
+ * module is not neceserraly enabled while upgrading, it is adviced to add the
+ * following lines in the begining of hook_update_N(), in order to make sure
+ * atleast the Entity API module is enabled.
+ *
+ * @code
+ *   if (!module_exists('entity')) {
+ *     // If Entity module isn't enabled we can't create the tables.
+ *     throw new DrupalUpdateException('You must enable Entity API module to perform this upgrade.');
+ *   }
+ * @endcode
  */
 function entity_exportable_schema_fields($module_col = 'module', $status_col = 'status') {
   return array(