Bug#856100: libav-tools : concat Protocol not found

[ça vaaa]

Package: libav-tools
Version: 6:11.8-1~deb8u1
Severity: normal

Dear Maintainer,

I'm trying to concatenate mp3 files using avconv (from libav-tools) with 
this line :

$ avconv -i 
concat:./The_Beach_Boys_-_God_Only_Knows.mp3\|./Order_Of_Era_-_one_is_the_loneliest_number.mp3 
-c copy /tmp/mix.mp3
avconv version 11.8-6:11.8-1~deb8u1, Copyright (c) 2000-2016 the Libav 
developers
   built on Oct  1 2016 07:16:29 with gcc 4.9.2 (Debian 4.9.2-10)

and I get :

concat:./The_Beach_Boys_-_God_Only_Knows.mp3|./Order_Of_Era_-_one_is_the_loneliest_number.mp3: 
Protocol not found

this protocol is listed in the manpage, but not showed by

$ avconv -protocols

thank you.

--

-- System Information:
Debian Release: 8.7
   APT prefers stable-updates
   APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 3.16.0-4-amd64 (SMP w/2 CPU cores)
Locale: LANG=fr_FR.UTF-8, LC_CTYPE=fr_FR.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages libav-tools depends on:
ii  dpkg             1.17.27
ii  libavcodec56     6:11.8-1~deb8u1
ii  libavdevice55    6:11.8-1~deb8u1
ii  libavfilter5     6:11.8-1~deb8u1
ii  libavformat56    6:11.8-1~deb8u1
ii  libavresample2   6:11.8-1~deb8u1
ii  libavutil54      6:11.8-1~deb8u1
ii  libc6            2.19-18+deb8u7
ii  libsdl1.2debian  1.2.15-10+b1
ii  libswscale3      6:11.8-1~deb8u1
ii  libvdpau1        0.8-3+deb8u2
ii  libx11-6         2:1.6.2-3

libav-tools recommends no packages.

Versions of packages libav-tools suggests:
pn  frei0r-plugins  <none>

-- no debconf information