diff --git a/libavcodec/snowenc.c b/libavcodec/snowenc.c
index 74749ae263..2142769dbd 100644
--- a/libavcodec/snowenc.c
+++ b/libavcodec/snowenc.c
@@ -725,6 +725,9 @@ static int get_dc(SnowEncContext *enc, int mb_x, int mb_y, int plane_index)
     }
     *b= backup;
 
+    if (!aa)
+        return 0;
+
     return av_clip_uint8( ROUNDED_DIV((int64_t)ab<<LOG2_OBMC_MAX, aa) ); //FIXME we should not need clipping
 }
 
diff --git a/tests/fate/filter-video.mak b/tests/fate/filter-video.mak
index 374e50b966..d16fff4d6c 100644
--- a/tests/fate/filter-video.mak
+++ b/tests/fate/filter-video.mak
@@ -54,6 +54,9 @@ FATE_FILTER_SAMPLES-$(call FILTERDEMDEC, MCDEINT, MPEGTS, MPEG2VIDEO, SNOW_ENCOD
 FATE_FILTER-$(call FILTERFRAMECRC, MCDEINT TESTSRC, SNOW_ENCODER) += fate-filter-mcdeint-slow-edge
 fate-filter-mcdeint-slow-edge: CMD = framecrc -auto_conversion_filters -flags bitexact -lavfi testsrc=s=5x32:r=25:d=1,mcdeint=mode=slow -frames:v 3
 
+FATE_FILTER-$(call FILTERFRAMECRC, MCDEINT TESTSRC, SNOW_ENCODER) += fate-filter-mcdeint-slow
+fate-filter-mcdeint-slow: CMD = framecrc -auto_conversion_filters -flags bitexact -lavfi testsrc=s=128x2:r=25:d=1,mcdeint=mode=slow -frames:v 3
+
 FATE_FILTER_SAMPLES-$(call FILTERDEMDEC, CODECVIEW, RM, RV40) += fate-filter-codecview-mvs
 fate-filter-codecview-mvs: CMD = framecrc -flags2 +export_mvs -i $(TARGET_SAMPLES)/real/spygames-2MB.rmvb -vf codecview=mv=pf+bf+bb -frames:v 60 -an
 
diff --git a/tests/ref/fate/filter-mcdeint-slow b/tests/ref/fate/filter-mcdeint-slow
new file mode 100644
index 0000000000..0888d44805
--- /dev/null
+++ b/tests/ref/fate/filter-mcdeint-slow
@@ -0,0 +1,8 @@
+#tb 0: 1/25
+#media_type 0: video
+#codec_id 0: rawvideo
+#dimensions 0: 128x2
+#sar 0: 1/1
+0,          0,          0,        1,      768, 0x6d637c68
+0,          1,          1,        1,      768, 0x07867cb0
+0,          2,          2,        1,      768, 0xa1ef7d04