diff --git a/README.md b/README.md
index 3b366d9..1bb43f0 100644
--- a/README.md
+++ b/README.md
@@ -93,6 +93,7 @@ Devise.setup do |config|
 
     # Sign up
     api.sign_up.enabled = true
+    api.sign_up.extra_fields = []
 
     # Authorization
     api.authorization.key = 'Authorization'
diff --git a/app/controllers/devise/api/tokens_controller.rb b/app/controllers/devise/api/tokens_controller.rb
index 9625d47..74f84c6 100644
--- a/app/controllers/devise/api/tokens_controller.rb
+++ b/app/controllers/devise/api/tokens_controller.rb
@@ -149,7 +149,7 @@ def refresh
       private
 
       def sign_up_params
-        params.permit(*resource_class.authentication_keys,
+        params.permit(*Devise.api.config.sign_up.extra_fields, *resource_class.authentication_keys,
                       *::Devise::ParameterSanitizer::DEFAULT_PERMITTED_ATTRIBUTES[:sign_up]).to_h
       end
 
diff --git a/lib/devise/api/configuration.rb b/lib/devise/api/configuration.rb
index 01360b0..424d2ea 100644
--- a/lib/devise/api/configuration.rb
+++ b/lib/devise/api/configuration.rb
@@ -22,6 +22,7 @@ class Configuration
 
       setting :sign_up, reader: true do
         setting :enabled, default: true, reader: true
+        setting :extra_fields, default: [], reader: true
       end
 
       setting :authorization, reader: true do
diff --git a/spec/devise/api/configuration_spec.rb b/spec/devise/api/configuration_spec.rb
index 8e0a18a..7decff4 100644
--- a/spec/devise/api/configuration_spec.rb
+++ b/spec/devise/api/configuration_spec.rb
@@ -52,6 +52,10 @@
       it 'enabled is true' do
         expect(config.sign_up.enabled).to eq true
       end
+
+      it 'extra_fields is an empty array' do
+        expect(config.sign_up.extra_fields).to eq []
+      end
     end
 
     context 'authorization' do