diff --git a/src/h2load.h b/src/h2load.h
index c65f3f0f..e01a3c8c 100644
--- a/src/h2load.h
+++ b/src/h2load.h
@@ -461,6 +461,7 @@ struct Client {
   int quic_handshake_completed();
   int quic_recv_stream_data(int64_t stream_id, int fin, const uint8_t *data,
                             size_t datalen);
+  int quic_acked_stream_data_offset(int64_t stream_id, size_t datalen);
   int quic_stream_close(int64_t stream_id, uint64_t app_error_code);
   int quic_stream_reset(int64_t stream_id, uint64_t app_error_code);
   int quic_extend_max_local_streams();
diff --git a/src/h2load_http3_session.cc b/src/h2load_http3_session.cc
index ca4bbe05..f15168c0 100644
--- a/src/h2load_http3_session.cc
+++ b/src/h2load_http3_session.cc
@@ -373,4 +373,13 @@ int Http3Session::add_write_offset(int64_t stream_id, size_t ndatalen) {
   return 0;
 }
 
+int Http3Session::add_ack_offset(int64_t stream_id, size_t datalen) {
+  auto rv = nghttp3_conn_add_ack_offset(conn_, stream_id, datalen);
+  if (rv != 0) {
+    client_->quic.last_error = quic::err_application(rv);
+    return -1;
+  }
+  return 0;
+}
+
 } // namespace h2load
diff --git a/src/h2load_http3_session.h b/src/h2load_http3_session.h
index f62b219d..48b4f80c 100644
--- a/src/h2load_http3_session.h
+++ b/src/h2load_http3_session.h
@@ -64,6 +64,7 @@ public:
                        size_t veccnt);
   int block_stream(int64_t stream_id);
   int add_write_offset(int64_t stream_id, size_t ndatalen);
+  int add_ack_offset(int64_t stream_id, size_t datalen);
 
 private:
   Client *client_;
diff --git a/src/h2load_quic.cc b/src/h2load_quic.cc
index c43ab310..984b0bd9 100644
--- a/src/h2load_quic.cc
+++ b/src/h2load_quic.cc
@@ -126,6 +126,26 @@ int Client::quic_recv_stream_data(int64_t stream_id, int fin,
   return 0;
 }
 
+namespace {
+int acked_stream_data_offset(ngtcp2_conn *conn, int64_t stream_id,
+                             uint64_t offset, size_t datalen, void *user_data,
+                             void *stream_user_data) {
+  auto c = static_cast<Client *>(user_data);
+  if (c->quic_acked_stream_data_offset(stream_id, datalen) != 0) {
+    return NGTCP2_ERR_CALLBACK_FAILURE;
+  }
+  return 0;
+}
+} // namespace
+
+int Client::quic_acked_stream_data_offset(int64_t stream_id, size_t datalen) {
+  auto s = static_cast<Http3Session *>(session.get());
+  if (s->add_ack_offset(stream_id, datalen) != 0) {
+    return -1;
+  }
+  return 0;
+}
+
 namespace {
 int stream_close(ngtcp2_conn *conn, int64_t stream_id, uint64_t app_error_code,
                  void *user_data, void *stream_user_data) {
@@ -331,7 +351,7 @@ int Client::quic_init(const sockaddr *local_addr, socklen_t local_addrlen,
       ngtcp2_crypto_hp_mask_cb,
       h2load::recv_stream_data,
       nullptr, // acked_crypto_offset
-      nullptr, // acked_stream_data_offset
+      h2load::acked_stream_data_offset,
       nullptr, // stream_open
       h2load::stream_close,
       nullptr, // recv_stateless_reset