diff --git a/libavcodec/sheervideo.c b/libavcodec/sheervideo.c
index 1a43727a30..d76963a1c7 100644
--- a/libavcodec/sheervideo.c
+++ b/libavcodec/sheervideo.c
@@ -2036,16 +2036,17 @@ static int decode_frame(AVCodecContext *avctx,
         return AVERROR_PATCHWELCOME;
     }
 
-    if (avpkt->size < 20 + avctx->width * avctx->height / 16) {
-        av_log(avctx, AV_LOG_ERROR, "Input packet too small\n");
-        return AVERROR_INVALIDDATA;
-    }
-
     if (s->format != format) {
-        if (ret < 0)
+        if (ret < 0) {
+            s->format = 0;
             return ret;
+        }
         s->format = format;
     }
+    if (avpkt->size < 20 + avctx->width * avctx->height / 16) {
+        av_log(avctx, AV_LOG_ERROR, "Input packet too small\n");
+        return AVERROR_INVALIDDATA;
+    }
 
     p->pict_type = AV_PICTURE_TYPE_I;
     p->key_frame = 1;