diff --git a/docs/designers-developers/developers/tutorials/metabox/meta-block-2-register-meta.md b/docs/designers-developers/developers/tutorials/metabox/meta-block-2-register-meta.md
index 744e50dfae5341..e444e07b40536d 100644
--- a/docs/designers-developers/developers/tutorials/metabox/meta-block-2-register-meta.md
+++ b/docs/designers-developers/developers/tutorials/metabox/meta-block-2-register-meta.md
@@ -35,3 +35,4 @@ register_post_meta( 'post', '_myguten_protected_key', array(
 	}
 ) );
 ```
+**Note:** Your post type needs to support `custom-fields` for `register_post_meta` function to work.
diff --git a/docs/designers-developers/developers/tutorials/sidebar-tutorial/plugin-sidebar-3-register-meta.md b/docs/designers-developers/developers/tutorials/sidebar-tutorial/plugin-sidebar-3-register-meta.md
index 999194e972bae7..afa859da1e35ca 100644
--- a/docs/designers-developers/developers/tutorials/sidebar-tutorial/plugin-sidebar-3-register-meta.md
+++ b/docs/designers-developers/developers/tutorials/sidebar-tutorial/plugin-sidebar-3-register-meta.md
@@ -19,3 +19,5 @@ wp.data.select( 'core/editor' ).getCurrentPost().meta;
 ```
 
 Before adding the `register_post_meta` function to the plugin, this code returns a void array, because WordPress hasn't been told to load any meta field yet. After registering the field, the same code will return an object containing the registered meta field you registered.
+
+If the code returns `undefined` make sure your post type supports `custom-fields`. Either when [registering the post](https://developer.wordpress.org/reference/functions/register_post_type/#supports) or with [add_post_type_support function](https://developer.wordpress.org/reference/functions/add_post_type_support/).