diff --git a/config/description.exs b/config/description.exs
index 509effbc3..df9f256ef 100644
--- a/config/description.exs
+++ b/config/description.exs
@@ -879,6 +879,14 @@
           2048
         ]
       },
+      %{
+        key: :registration_reason_length,
+        type: :integer,
+        description: "Maximum registration reason length. Default: 500.",
+        suggestions: [
+          500
+        ]
+      },
       %{
         key: :external_user_synchronization,
         type: :boolean,
diff --git a/docs/configuration/cheatsheet.md b/docs/configuration/cheatsheet.md
index 5cf073293..c89df24cc 100644
--- a/docs/configuration/cheatsheet.md
+++ b/docs/configuration/cheatsheet.md
@@ -59,6 +59,7 @@ To add configuration to your config file, you can copy it from the base config.
 * `max_remote_account_fields`: The maximum number of custom fields in the remote user profile (default: `20`).
 * `account_field_name_length`: An account field name maximum length (default: `512`).
 * `account_field_value_length`: An account field value maximum length (default: `2048`).
+* `registration_reason_length`: Maximum registration reason length (default: `500`).
 * `external_user_synchronization`: Enabling following/followers counters synchronization for external users.
 * `cleanup_attachments`: Remove attachments along with statuses. Does not affect duplicate files and attachments without status. Enabling this will increase load to database when deleting statuses on larger instances.