diff --git a/lib/signature.rb b/lib/signature.rb
index 319aafc..48777bf 100644
--- a/lib/signature.rb
+++ b/lib/signature.rb
@@ -90,13 +90,10 @@ def auth_hash
     private
 
       def signature(token)
+        digest = OpenSSL::Digest::SHA256.new
         OpenSSL::HMAC.hexdigest(digest, token.secret, string_to_sign)
       end
 
-      def digest
-        OpenSSL::Digest::Digest.new('sha256')
-      end
-
       def string_to_sign
         [@method, @path, parameter_string].join("\n")
       end