diff --git a/libavcodec/c93.c b/libavcodec/c93.c
index c51f2fa9de..bb44f38791 100644
--- a/libavcodec/c93.c
+++ b/libavcodec/c93.c
@@ -127,6 +127,8 @@ static int decode_frame(AVCodecContext *avctx, void *data,
     uint8_t *out;
     int stride, ret, i, x, y, b, bt = 0;
 
+    avcodec_set_dimensions(avctx, WIDTH, HEIGHT);
+
     c93->currentpic ^= 1;
 
     if ((ret = ff_reget_buffer(avctx, newpic)) < 0)