diff --git a/libavcodec/dnxhdenc.c b/libavcodec/dnxhdenc.c
index b5d62bf9a1..690e64f869 100644
--- a/libavcodec/dnxhdenc.c
+++ b/libavcodec/dnxhdenc.c
@@ -272,6 +272,7 @@ static int dnxhd_encode_init(AVCodecContext *avctx)
     av_log(avctx, AV_LOG_DEBUG, "cid %d\n", ctx->cid);
 
     index = ff_dnxhd_get_cid_table(ctx->cid);
+    av_assert0(index >= 0);
     ctx->cid_table = &ff_dnxhd_cid_table[index];
 
     ctx->m.avctx = avctx;