diff --git a/lib/sinatra/base.rb b/lib/sinatra/base.rb
index 1d46a8d5..8e42d9cd 100644
--- a/lib/sinatra/base.rb
+++ b/lib/sinatra/base.rb
@@ -949,6 +949,7 @@ module Sinatra
       res = catch(:halt) { yield }
       res = [res] if Fixnum === res or String === res
       if Array === res and Fixnum === res.first
+        res = res.dup
         status(res.shift)
         body(res.pop)
         headers(*res)