extensions.conf: exten => s,n,Dial(SIP/205,6,r)

asterisk's output (does work fine):

    -- Executing Dial("Zap/6-1", "SIP/205|6|r") in new stack
    -- Called 205
    -- SIP/205-bb77 is ringing
    -- Nobody picked up in 6000 ms
    -- Hungup 'Zap/6-1'


extensions.conf: exten => s,n,Dial(Zap/G1/${s_phone},6,r)

asterisk's output (doesn't work as it should):

    -- Executing Dial("Zap/6-1", "Zap/G1/07966016252|6|r") in new stack
    -- Called G1/07966016252
    -- Zap/7-1 answered Zap/6-1
    -- Attempting native bridge of Zap/6-1 and Zap/7-1
    -- Hungup 'Zap/7-1'
  == Spawn extension (shq-ip-s-a-h, s, 4) exited non-zero on 'Zap/6-1'
    -- Hungup 'Zap/6-1'