diff --git a/config.yml b/config.yml
index 00d2400..9104173 100644
--- a/config.yml
+++ b/config.yml
@@ -37,7 +37,7 @@ smtp_authentication: plain
 smtp_enable_starttls: yes
 smtp_openssl_verify_mode: peer
 swap_add_mb: 512
-ruby_version: 2.7.1
+ruby_version: 2.6.6
 is_production_vm: no
 redmine_files_nfs_mount: ''  # /mnt/redminefiles
 redmine_files_nfs_source: '' # 171.26.20.75:/srv/easyredmine