diff --git a/CHANGELOG.md b/CHANGELOG.md
index a6639b5..53d1152 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,18 @@
 <!-- This file is generated, please add to it using `knope document-change` in the client-library-templates repo -->
 # Changelog
 
+## 4.20.1 (2026-10-13)
+
+### Fixes
+
+#### Fix crash on string error bodies and unrecognised error types
+
+Error responses whose `error` is a plain string, with a status other than 400, 401, 403 or 429 (for example a 404 or 422), previously raised `NoMethodError: undefined method 'to_sym' for nil` instead of a GoCardless error. They now raise `GoCardlessPro::ApiError` with the message from the response.
+
+Error responses with an unrecognised `type` now also raise `GoCardlessPro::ApiError` instead of `KeyError`.
+
+`code` is now set to the HTTP status for string error bodies. It was previously `nil`.
+
 ## 4.20.0 (2026-10-12)
 
 ### Features
diff --git a/lib/gocardless_pro/client.rb b/lib/gocardless_pro/client.rb
index cb9b7cf..79e97ac 100644
--- a/lib/gocardless_pro/client.rb
+++ b/lib/gocardless_pro/client.rb
@@ -283,7 +283,7 @@ def default_options
           'User-Agent' => "#{user_agent}",
           'Content-Type' => 'application/json',
           'GoCardless-Client-Library' => 'gocardless-pro-ruby',
-          'GoCardless-Client-Version' => '4.20.0',
+          'GoCardless-Client-Version' => '4.20.1',
         },
       }
     end
diff --git a/lib/gocardless_pro/version.rb b/lib/gocardless_pro/version.rb
index 4a9c49f..658627a 100644
--- a/lib/gocardless_pro/version.rb
+++ b/lib/gocardless_pro/version.rb
@@ -3,5 +3,5 @@ module GoCardlessPro
 
 module GoCardlessPro
   # Current version of the GC gem
-  VERSION = '4.20.0'
+  VERSION = '4.20.1'
 end