Start and debug remote application doesn’t set sysroot variable

Hi,
Until I switch from QtCreator 2.2.1 to QtCreator 2.5.1, I could remotly debug my application, with is on an nfs system.
But since I used QtCreator 2.5.1, variable sysroot from “Start and debug remote application” widget doesn’t seem to be set, because gdb doesn’t find some librairies of the system on the nfs…
Is there specific variable to set in the gdb tool-chain in Tools > Options > Build&Run >Tool&Chains?

Thanks in advance