diff --git a/src/Hash/HMAC_SHA1.php b/src/Hash/HMAC_SHA1.php
index 900251a..d6d19ed 100644
--- a/src/Hash/HMAC_SHA1.php
+++ b/src/Hash/HMAC_SHA1.php
@@ -28,7 +28,7 @@ class HMAC_SHA1 implements HashInterface
     /** @SuppressWarnings(PHPMD.StaticAccess) */
     public static function keygen(): string
     {
-        return Base32::encodeUpper(random_bytes(this::DEFAULT_SECRET_SIZE));
+        return Base32::encodeUpper(random_bytes(self::DEFAULT_SECRET_SIZE));
     }
 }