diff --git a/classes/module/Module.php b/classes/module/Module.php
index 422c9a7ea..156a7b0ef 100644
--- a/classes/module/Module.php
+++ b/classes/module/Module.php
@@ -400,10 +400,10 @@ abstract class ModuleCore
 		// Check the version of the module with the registered one and look if any upgrade file exist
 		if (Tools::version_compare($module->version, $module->database_version, '>'))
 		{
-			$oldVersion = $module->database_version;
+			$old_version = $module->database_version;
 			$module = Module::getInstanceByName($module->name);
 			if ($module instanceof Module)
-				return $module->loadUpgradeVersionList($module->name, $module->version, $oldVersion);
+				return $module->loadUpgradeVersionList($module->name, $module->version, $old_version);
 		}
 		return null;
 	}