Drop down in connect time between 9.3.6 and 9.3.9 ?

Hello,
We've just upgraded some productive servers from 9.3.6 to 9.3.9, and it seems that the time to get a connection (or
possiblyto disconnect) has become much slower. 
These tests are consistent when run against different servers.

tests with 9.4.1 show fast times, but we don't have a later version to test yet.

Is this a known issue ?

    9.3.6:
    time { i=0; while [ $i -lt 1000 ]; do let i++; psql -c 'select 1' ; done; } >/dev/null

    real    0m4.994s
    user    0m0.088s
    sys     0m0.272s

    9.3.9:
    time { i=0; while [ $i -lt 1000 ]; do let i++; psql -c 'select 1' ; done; } >/dev/null

    real    0m11.081s
    user    0m0.140s
    sys     0m0.208s

regards,

Marc Mamin