diff --git a/libavcodec/h264_slice.c b/libavcodec/h264_slice.c
index a560027ee4..8c3b9f354c 100644
--- a/libavcodec/h264_slice.c
+++ b/libavcodec/h264_slice.c
@@ -1410,13 +1410,15 @@ int ff_h264_decode_slice_header(H264Context *h, H264Context *h0)
                      || 16*h->sps.mb_height * (2 - h->sps.frame_mbs_only_flag) != h->avctx->coded_height
                      || h->avctx->bits_per_raw_sample != h->sps.bit_depth_luma
                      || h->cur_chroma_format_idc != h->sps.chroma_format_idc
-                     || av_cmp_q(h->sps.sar, h->avctx->sample_aspect_ratio)
                      || h->mb_width  != h->sps.mb_width
                      || h->mb_height != h->sps.mb_height * (2 - h->sps.frame_mbs_only_flag)
                     ));
     if (non_j_pixfmt(h0->avctx->pix_fmt) != non_j_pixfmt(get_pixel_format(h0, 0)))
         must_reinit = 1;
 
+    if (first_slice && av_cmp_q(h->sps.sar, h->avctx->sample_aspect_ratio))
+        must_reinit = 1;
+
     h->mb_width  = h->sps.mb_width;
     h->mb_height = h->sps.mb_height * (2 - h->sps.frame_mbs_only_flag);
     h->mb_num    = h->mb_width * h->mb_height;