Lighttpd

I'm using latest lighttpd.git branch stbuehler (with small modifications), and found that mod_cgi refuse to serve some of my requests - gives Bad Gateway.
Compiled with gcc version 4.2.3 (Debian 4.2.3-1)
Here is my configuration:

var.PID              = 17495
var.CWD              = "/root" 
server.modules       = (
    "mod_indexfile",
    "mod_rewrite",
    "mod_access",
    "mod_uploadprogress",
    "mod_auth",
    "mod_setenv",
    "mod_accesslog",
    "mod_proxy_core",
    "mod_proxy_backend_fastcgi",
    "mod_cgi",
    "mod_dirlisting",
    "mod_staticfile",
    "mod_chunked",
    # 13
)
server.document-root = "/var/www/" 
server.errorlog      = "/var/log/lighttpd/error.log" 
server.indexfiles    = ("index.php", "index.html", "index.htm", "default.htm")
accesslog.filename   = "/var/log/lighttpd/access.log" 
url.access-deny      = ("~", ".inc")
server.pid-file      = "/var/run/lighttpd.pid" 
server.dir-listing   = "disable" 
server.username      = "www-data" 
server.groupname     = "www-data" 

$PHYSICAL["existing-path"] =~ "\.php$" {
    # block 1
    proxy-core.balancer         = "round-robin" 
    proxy-core.protocol         = "fastcgi" 
    proxy-core.allow-x-sendfile = "enable" 
    proxy-core.backends         = ("unix:/tmp/php-fastcgi.sock")
    proxy-core.max-pool-size    = 16

} # end of $PHYSICAL["existing-path"] =~ "\.php$" 

$HTTP["url"] == "/php5-cgi.php" {
    # block 2
    proxy-core.backends = ()
    cgi.assign          = (
        ".php" => "/usr/bin/php5-cgi",
    )

} # end of $HTTP["url"] == "/php5-cgi.php" 

and example output from wget

for i in `seq 1 4`; do wget -S -O /dev/null http://192.168.0.91/php5-cgi.php 2>&1 | grep "^\ \ HTTP"; done
  HTTP/1.0 502 Bad Gateway
  HTTP/1.0 502 Bad Gateway
  HTTP/1.0 200 OK
  HTTP/1.0 200 OK

error.log contents

http_resp.c.302: (error) invalid status code -1
mod_cgi.c.319: (trace) response parser failed
http_resp.c.302: (error) invalid status code -1
mod_cgi.c.319: (trace) response parser failed

and the source of php5-cgi.php

<?
        print('asdf');
?>

but when i use fastcgi the problem goes away /source of php5-fastcgi.php is the same as php5-cgi.php/

for i in `seq 1 4`; do wget -S -O /dev/null http://192.168.0.91/php5-fastcgi.php 2>&1 | grep "^\ \ HTTP"; done
  HTTP/1.0 200 OK
  HTTP/1.0 200 OK
  HTTP/1.0 200 OK
  HTTP/1.0 200 OK