Hi Maxim, I stripped down my configuration and removed 'unneeded' parts to reproduce.
I'm able to reproduce it with the following settings: location / { # Added to mitigate the issue. Removed for testing #rewrite ^/index.html$ / break; proxy_pass http://backends; proxy_next_upstream error timeout invalid_header; proxy_buffering on; proxy_connect_timeout 1; proxy_read_timeout 30; proxy_cache_background_update on; proxy_http_version 1.1; proxy_set_header Connection ""; proxy_cache STATIC; proxy_cache_use_stale error timeout invalid_header updating http_500 http_502 http_503 http_504; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header Accept-Encoding ""; set $no_cache ""; proxy_ignore_headers Cache-Control Expires Vary; # Removing the if construction and leaving the "expires" in place solves the issue! if ($no_cache = "") { expires 1s; } proxy_cache_valid 200 3s; } To test the call I used curl and wget: curl --verbose --header "host: www.example.com" -o /dev/null http://1.2.3.4/ wget --header "host: www.example.com" --output-document=/dev/null http://1.2.3.4/ The Apache logs show: example.com 1.2.3.4 127.0.0.1 - - [26/Feb/2017:18:49:17 +0100] "GET /index.html HTTP/1.1" 404 43193 "-" "curl/7.26.0" example.com 1.2.3.4 127.0.0.1 - - [26/Feb/2017:18:53:22 +0100] "GET /index.html HTTP/1.1" 404 43194 "-" "Wget/1.13.4 (linux-gnu)" I captured traffic using tcpdump and Wireshark shows the following: Original request with curl GET / HTTP/1.1 User-Agent: curl/7.26.0 Accept: */* host: www.example.com Resulting request from Nginx: GET /index.html HTTP/1.1 Host: www.example.com X-Real-IP: 1.2.3.4 X-Forwarded-For: 1.2.3.4 User-Agent: curl/7.26.0 Accept: */* HTTP/1.1 404 Not Found Date: Sun, 26 Feb 2017 18:04:24 GMT Server: Apache Thanks in advance, JP Posted at Nginx Forum: https://forum.nginx.org/read.php?2,272622,272629#msg-272629 _______________________________________________ nginx mailing list nginx@nginx.org http://mailman.nginx.org/mailman/listinfo/nginx