No sound encoding to MJPG

Source video:
Video: CRAM 320x240 24fps 9221kbps [V: msvideo1, pal8, 320x240, 9221 kb/s]
Audio: PCM 48000Hz stereo 1536kbps [A: pcm_s16le, 48000 Hz, 2 channels, s16, 1536 kb/s]

Encoding goal:
Video: MJPG 320x240 21.682fps 2473kbps [V: mjpeg, yuvj420p, 320x240, * kb/s]
Audio: IMA ADPCM *Hz mono *kbps [A: adpcm_ima_wav, * Hz, 1 channels, s16, * kb/s]

Command:
ffmpeg.exe -i Naamloos_4.avi -vcodec mjpeg -q:v 1 -acodec adpcm_ima_wav -an output.avi


Problems:
No audio in the output file, ffmpeg doesn't seem to write anything either(audio:0kB)

Output:
ffmpeg version N-70580-g399e314 Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 4.9.2 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r
ray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-
b --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora -
enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-
le-zlib
  libavutil      54. 20.100 / 54. 20.100
  libavcodec     56. 26.100 / 56. 26.100
  libavformat    56. 25.101 / 56. 25.101
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 12.100 /  5. 12.100
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
Guessed Channel Layout for  Input Stream #0.1 : stereo
Input #0, avi, from 'Naamloos_4.avi':
  Duration: 00:01:17.25, start: 0.000000, bitrate: 10758 kb/s
    Stream #0:0: Video: msvideo1 (CRAM / 0x4D415243), pal8, 320x240, 9221 kb/s, 24 fps, 24 tbr, 24 tbn, 24 tbc
    Stream #0:1: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 48000 Hz, 2 channels, s16, 1536 kb/s
File 'output.avi' already exists. Overwrite ? [y/N] y
[swscaler @ 0291e440] deprecated pixel format used, make sure you did set range correctly
Output #0, avi, to 'output.avi':
  Metadata:
    ISFT            : Lavf56.25.101
    Stream #0:0: Video: mjpeg (MJPG / 0x47504A4D), yuvj444p(pc), 320x240, q=2-31, 200 kb/s, 24 fps, 24 tbn, 24 tbc
    Metadata:
      encoder         : Lavc56.26.100 mjpeg
Stream mapping:
  Stream #0:0 -> #0:0 (msvideo1 (native) -> mjpeg (native))
Press [q] to stop, [?] for help
frame= 1854 fps=1425 q=0.0 Lsize=   56390kB time=00:01:17.25 bitrate=5979.9kbits/s
video:56340kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.088569%