diff --git a/libavcodec/ffv1dec.c b/libavcodec/ffv1dec.c
index d2bfee784fb36155680d72164546e4672c2765c2..5eadb6b158648c4ae796fd37617c6e94e5ff87dd 100644
--- a/libavcodec/ffv1dec.c
+++ b/libavcodec/ffv1dec.c
@@ -717,7 +717,7 @@ static int read_header(FFV1Context *f)
     } else {
         const uint8_t *p = c->bytestream_end;
         for (f->slice_count = 0;
-             f->slice_count < MAX_SLICES && 3 < p - c->bytestream_start;
+             f->slice_count < MAX_SLICES && 3 + 5*!!f->ec < p - c->bytestream_start;
              f->slice_count++) {
             int trailer = 3 + 5*!!f->ec;
             int size = AV_RB24(p-trailer);