diff --git a/lib/httparty/net_digest_auth.rb b/lib/httparty/net_digest_auth.rb
index 20311ee..82ac344 100644
--- a/lib/httparty/net_digest_auth.rb
+++ b/lib/httparty/net_digest_auth.rb
@@ -92,7 +92,7 @@ module Net
       end
 
       def random
-        "%x" % (Time.now.to_i + rand(65535))
+        format "%x", (Time.now.to_i + rand(65535))
       end
 
       def request_digest
diff --git a/lib/httparty/response.rb b/lib/httparty/response.rb
index 8e8a55e..65fe24b 100644
--- a/lib/httparty/response.rb
+++ b/lib/httparty/response.rb
@@ -37,7 +37,7 @@ module HTTParty
     end
 
     def inspect
-      inspect_id = "%x" % (object_id * 2)
+      inspect_id = format "%x", (object_id * 2)
       %(#<#{self.class}:0x#{inspect_id} parsed_response=#{parsed_response.inspect}, @response=#{response.inspect}, @headers=#{headers.inspect}>)
     end