diff --git a/libavcodec/h264_slice.c b/libavcodec/h264_slice.c
index d8b7bc7fa9..b3fdc992e6 100644
--- a/libavcodec/h264_slice.c
+++ b/libavcodec/h264_slice.c
@@ -1454,6 +1454,7 @@ int ff_h264_decode_slice_header(H264Context *h, H264Context *h0)
 
     if (h->context_initialized &&
         (must_reinit || needs_reinit)) {
+        h->context_initialized = 0;
         if (h != h0) {
             av_log(h->avctx, AV_LOG_ERROR,
                    "changing width %d -> %d / height %d -> %d on "