diff --git a/src/Log/DrushLoggerManager.php b/src/Log/DrushLoggerManager.php
index bb7a8422de..18690cc185 100644
--- a/src/Log/DrushLoggerManager.php
+++ b/src/Log/DrushLoggerManager.php
@@ -9,6 +9,6 @@ class DrushLoggerManager extends LoggerManager implements SuccessInterface
 {
     public function success(string $message, array $context = array())
     {
-        $this->log(ConsoleLogLevel::SUCCESS, $message, $context);
+        $this->log(self::SUCCESS, $message, $context);
     }
 }
diff --git a/src/Log/SuccessInterface.php b/src/Log/SuccessInterface.php
index ed3cab36e4..e72c9952da 100644
--- a/src/Log/SuccessInterface.php
+++ b/src/Log/SuccessInterface.php
@@ -4,6 +4,12 @@
 
 interface SuccessInterface
 {
+    /**
+     * Command successfully completed some operation.
+     * Displayed at VERBOSITY_NORMAL.
+     */
+    public const SUCCESS = 'success';
+
     /**
      * Log a 'success' message.
      */