[squid-users] Please help debugging proxy problem with GET /

Hi folks,
We get the following problem with Squid configuration. Short GET or POST requests do not pass proxy, the proxy returns customized "invalid request" error message

GET / HTTP/1.0\r\n
Host: yandex.ru\r\n
Proxy-Authorization: Basic ***\r\n
\r\n

The following works:

GET http://yandex.ru/ HTTP/1.0\r\n
Host: yandex.ru\r\n
Proxy-Authorization: Basic ***\r\n
\r\n

Where to start digging? Thank you in advance!

--
С уважением, Алексей Федотов,
эксперт  по управлению ИТ-рисками ФСК ЕЭС
+7 916 562 8095