502 Bad Gateway: upstream sent too big header while reading response header from upstream, client: 127.0.0.1

I've tried increasing the buffer sizes as suggested in other threads.

Here is the output of

sudo nginx -T | grep buffer

fastcgi_buffer_size 4096k;
fastcgi_buffers 128 4096k;
fastcgi_busy_buffers_size 4096k;
proxy_buffer_size   4096k;
proxy_buffers   128 4096k;
proxy_busy_buffers_size   4096k;

I've restarted valet but I am still getting the error when submitting a POST request after adding something to my cart using darryldecode/laravelshoppingcart. The redirect after adding the second item to the shoppingcart causes the 502 error.

Any suggestions?

Thanks in advance!