diff --git a/lib/puma/commonlogger.rb b/lib/puma/commonlogger.rb
index b37d0dc6..69448d07 100644
--- a/lib/puma/commonlogger.rb
+++ b/lib/puma/commonlogger.rb
@@ -61,7 +61,7 @@ module Puma
         now.strftime("%d/%b/%Y %H:%M:%S"),
         env[REQUEST_METHOD],
         env[PATH_INFO],
-        env[QUERY_STRING].empty? ? "" : "?"+env[QUERY_STRING],
+        env[QUERY_STRING].empty? ? "" : "?#{env[QUERY_STRING]}",
         env["HTTP_VERSION"],
         now - began_at ]
     end
@@ -76,7 +76,7 @@ module Puma
         now.strftime("%d/%b/%Y:%H:%M:%S %z"),
         env[REQUEST_METHOD],
         env[PATH_INFO],
-        env[QUERY_STRING].empty? ? "" : "?"+env[QUERY_STRING],
+        env[QUERY_STRING].empty? ? "" : "?#{env[QUERY_STRING]}",
         env["HTTP_VERSION"],
         status.to_s[0..3],
         length,