Thin crashes with numeric headers

[fabn]

I have an around_action in my controller that write an header with a numeric value in this way

elapsed = Benchmark.realtime(&action)
headers['X-Report-Runtime'] = elapsed

This is causing an error in thin, at this line because obviously numeric values do not respond to each.

I don't know if it's unsupported by rack to add numeric values as header values but with other rack servers that code is working.