diff --git a/libavcodec/ffv1dec.c b/libavcodec/ffv1dec.c
index 6e23f8799f..ea04e0bc75 100644
--- a/libavcodec/ffv1dec.c
+++ b/libavcodec/ffv1dec.c
@@ -362,7 +362,7 @@ static int decode_slice(AVCodecContext *c, void *arg)
     if (fs->ac != AC_GOLOMB_RICE && f->version > 2) {
         int v;
         get_rac(&fs->c, (uint8_t[]) { 129 });
-        v = fs->c.bytestream_end - fs->c.bytestream - 2 - 5*f->ec;
+        v = fs->c.bytestream_end - fs->c.bytestream - 2 - 5*!!f->ec;
         if (v) {
             av_log(f->avctx, AV_LOG_ERROR, "bytestream end mismatching by %d\n", v);
             fs->slice_damaged = 1;