diff --git a/Dockerfile b/Dockerfile
index c94cb65..e3029e2 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -38,6 +38,7 @@ RUN cd /tmp \
     && cd .. \
     && rm -rf fftw-3.3.8
 
+# required by hvf.Deblock_QED (required by fvf.AutoDeblock)
 RUN cd /tmp \
     && git clone --depth=1 https://github.com/HomeOfVapourSynthEvolution/VapourSynth-DCTFilter \
     && cd VapourSynth-DCTFilter \