Logging request headers in nginx

I want to log custom headers from clients requests. I have added "$http_my_header" to my log_format and it is logged nicely for POST requests. All GET request, on the other hand, a logged with empty value. The example of GET request: GET /pws HTTP/1.1 upgrade: websocket connection: Upgrade sec-websocket-key: XXXX host: XXXX sec-websocket-origin: XXXX sec-websocket-version: 13 X-Plumbr-sessionId: XXXX X-Plumbr-accountId: XXXX X-Plumbr-build: SNAPSHOT My nginx log_format contains "$http_x_plumbr_accountid" "$http_x_plumbr_build" Does logging headers in GET requests require some special configuration?