diff --git a/libavcodec/h264_redundant_pps_bsf.c b/libavcodec/h264_redundant_pps_bsf.c
index a8af4105cf..cf41abe96c 100644
--- a/libavcodec/h264_redundant_pps_bsf.c
+++ b/libavcodec/h264_redundant_pps_bsf.c
@@ -41,8 +41,19 @@ typedef struct H264RedundantPPSContext {
 
 
 static int h264_redundant_pps_fixup_pps(H264RedundantPPSContext *ctx,
-                                        H264RawPPS *pps)
+                                        CodedBitstreamUnit *unit)
 {
+    H264RawPPS *pps;
+    int err;
+
+    // The changes we are about to perform affect the parsing process,
+    // so we must make sure that the PPS is writable, otherwise the
+    // parsing of future slices will be incorrect and even raise errors.
+    err = ff_cbs_make_unit_writable(ctx->input, unit);
+    if (err < 0)
+        return err;
+    pps = unit->content;
+
     // Record the current value of pic_init_qp in order to fix up
     // following slices, then overwrite with the global value.
     ctx->current_pic_init_qp = pps->pic_init_qp_minus26 + 26;
@@ -89,7 +100,7 @@ static int h264_redundant_pps_filter(AVBSFContext *bsf, AVPacket *pkt)
         if (nal->type == H264_NAL_SPS)
             au_has_sps = 1;
         if (nal->type == H264_NAL_PPS) {
-            err = h264_redundant_pps_fixup_pps(ctx, nal->content);
+            err = h264_redundant_pps_fixup_pps(ctx, nal);
             if (err < 0)
                 goto fail;
             if (!au_has_sps) {
@@ -145,7 +156,7 @@ static int h264_redundant_pps_init(AVBSFContext *bsf)
 
         for (i = 0; i < au->nb_units; i++) {
             if (au->units[i].type == H264_NAL_PPS) {
-                err = h264_redundant_pps_fixup_pps(ctx, au->units[i].content);
+                err = h264_redundant_pps_fixup_pps(ctx, &au->units[i]);
                 if (err < 0)
                     goto fail;
             }