diff --git a/lib/omniauth/strategies/yahoo_oauth2.rb b/lib/omniauth/strategies/yahoo_oauth2.rb
index 4af6032..4072b7e 100644
--- a/lib/omniauth/strategies/yahoo_oauth2.rb
+++ b/lib/omniauth/strategies/yahoo_oauth2.rb
@@ -5,7 +5,7 @@ module OmniAuth
   module Strategies
     class YahooOauth2 < OmniAuth::Strategies::OAuth2
       option :name, 'yahoo_oauth2'
-      
+
       option :client_options, {
         site: 'https://api.login.yahoo.com',
         authorize_url: '/oauth2/request_auth',
@@ -30,16 +30,15 @@ class YahooOauth2 < OmniAuth::Strategies::OAuth2
 
       def build_access_token
         verifier = request.params['code']
-        
+
         auth = "Basic #{Base64.strict_encode64("#{options.client_id}:#{options.client_secret}")}"
-        
+
         token = client.get_token(
           { redirect_uri: callback_url, code: verifier, grant_type: 'authorization_code', headers: { 'Authorization' => auth } }.
-          merge(token_params.to_hash(symbolize_keys: true)), deep_symbolize(options.auth_token_params))
-        
+          merge(token_params.to_hash(symbolize_keys: true)), deep_symbolize(options.auth_token_params || {}))
         token
       end
-      
+
       def raw_info
         raw_info_url = "https://social.yahooapis.com/v1/user/#{uid}/profile?format=json"
         @raw_info ||= access_token.get(raw_info_url).parsed