diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2535d61bb..edc7c81b5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ User-visible changes worth mentioning.
 
 Add your entry here.
 
+- [#1715] Fix token introspection invalid request reason
 - [#1714] Fix `Doorkeeper::AccessToken.find_or_create_for` with empty scopes which raises NoMethodError
 - [#1712] Add `Pragma: no-cache` to token response
 
diff --git a/lib/doorkeeper/oauth/token_introspection.rb b/lib/doorkeeper/oauth/token_introspection.rb
index 4dca014ef..002c73cb0 100644
--- a/lib/doorkeeper/oauth/token_introspection.rb
+++ b/lib/doorkeeper/oauth/token_introspection.rb
@@ -6,7 +6,7 @@ module OAuth
     #
     # @see https://datatracker.ietf.org/doc/html/rfc7662
     class TokenIntrospection
-      attr_reader :error
+      attr_reader :error, :invalid_request_reason
 
       def initialize(server, token)
         @server = server
@@ -38,7 +38,6 @@ def to_json(*)
       private
 
       attr_reader :server, :token
-      attr_reader :invalid_request_reason
 
       # If the protected resource uses OAuth 2.0 client credentials to
       # authenticate to the introspection endpoint and its credentials are
diff --git a/spec/controllers/tokens_controller_spec.rb b/spec/controllers/tokens_controller_spec.rb
index 012c18622..9d029314a 100644
--- a/spec/controllers/tokens_controller_spec.rb
+++ b/spec/controllers/tokens_controller_spec.rb
@@ -536,7 +536,7 @@
 
         expect(json_response).to match(
           "error" => "invalid_request",
-          "error_description" => an_instance_of(String),
+          "error_description" => I18n.t("doorkeeper.errors.messages.invalid_request.request_not_authorized"),
         )
       end
     end