Why does Safari does not allow trailing space in header value

We need a context for this, a link and / or screen shot, a full description of the error and a look at the underlying code.

Hi,
I have attached the screenshot of safari console tab. Here if i give a trailing space at the end of a request header it throws an exception otherwise it just runs fine...
Screen-Shot-2016-10-06-at-11.11.17-A.png

Still not enough - we need to see the code.

Sidebar - is the space on the end necessary - why not simply trim it before sending.

Thats the whole code in the screenshot just create an xhr request and add an header with a trailing space at the end... It throws an error this does not happen in chrome.. or firefox...
Yes thats what i am planning to do just trim the space before sending....
Just wanted to know if there is any possible reason why safari has done that  and not chrome...