diff --git a/_config.yml b/_config.yml
index c2168421..e1ca7a42 100644
--- a/_config.yml
+++ b/_config.yml
@@ -83,8 +83,8 @@ index_old_doc_paths: false
 # drop-down list in the distro selector.
 #
 ros2_distros:
+  - 'crystal'
   - 'bouncy'
-  - 'ardent'
 
 ros_distros:
   - 'melodic'
@@ -92,7 +92,8 @@ ros_distros:
   - 'kinetic'
   - 'indigo'
 
-old_ros2_distros: []
+old_ros2_distros:
+  - 'ardent'
 
 old_ros_distros:
   - 'jade'