svg sequence pipe

works:

ffmpeg -i images/image-%02d.svg video.mp4

does not work:

cat images/*.svg | ffmpeg -f image2pipe -c:v svg -i - video.mp4

error:

ffmpeg version N-88409-ga8305b0ea3 Copyright (c) 2000-2017 the FFmpeg developers
  built with Apple LLVM version 9.0.0 (clang-900.0.37)
  configuration: --prefix=./bin --enable-gpl --enable-nonfree --enable-librsvg --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libopus --enable-libxvid
  libavutil      56.  0.100 / 56.  0.100
  libavcodec     58.  1.100 / 58.  1.100
  libavformat    58.  0.102 / 58.  0.102
  libavdevice    58.  0.100 / 58.  0.100
  libavfilter     7.  0.101 /  7.  0.101
  libswscale      5.  0.101 /  5.  0.101
  libswresample   3.  0.100 /  3.  0.100
  libpostproc    55.  0.100 / 55.  0.100
[image2pipe @ 0x7fe0d1800000] Could not find codec parameters for stream 0 (Video: svg (librsvg), none): unspecified size
Consider increasing the value for the 'analyzeduration' and 'probesize' options
Input #0, image2pipe, from 'pipe:':
  Duration: N/A, bitrate: N/A
    Stream #0:0: Video: svg, none, 25 tbr, 25 tbn, 25 tbc
Output #0, mp4, to 'video.mp4':
Output file #0 does not contain any stream