diff --git a/doc/Makefile.am b/doc/Makefile.am
index ba5b7888..a1a177e8 100644
--- a/doc/Makefile.am
+++ b/doc/Makefile.am
@@ -107,6 +107,7 @@ APIDOCS= \
 	nghttp2_session_callbacks_set_send_callback.rst \
 	nghttp2_session_callbacks_set_send_data_callback.rst \
 	nghttp2_session_callbacks_set_unpack_extension_callback.rst \
+	nghttp2_session_change_extpri_stream_priority.rst \
 	nghttp2_session_change_stream_priority.rst \
 	nghttp2_session_check_request_allowed.rst \
 	nghttp2_session_check_server_session.rst \
diff --git a/lib/includes/nghttp2/nghttp2.h b/lib/includes/nghttp2/nghttp2.h
index effed7ff..2e87c481 100644
--- a/lib/includes/nghttp2/nghttp2.h
+++ b/lib/includes/nghttp2/nghttp2.h
@@ -4901,6 +4901,40 @@ NGHTTP2_EXTERN int nghttp2_submit_priority_update(nghttp2_session *session,
                                                   const uint8_t *field_value,
                                                   size_t field_value_len);
 
+/**
+ * @function
+ *
+ * Changes the priority of the existing stream denoted by |stream_id|.
+ * The new priority is |extpri|.  This function is meant to be used by
+ * server for :rfc:`9218` extensible prioritization scheme.
+ *
+ * If |session| is initialized as client, this function returns
+ * :enum:`nghttp2_error.NGHTTP2_ERR_INVALID_STATE`.  For client, use
+ * `nghttp2_submit_priority_update()` instead.
+ *
+ * If :member:`extpri->urgency <nghttp2_extpri.urgency>` is out of
+ * bound, it is set to :macro:`NGHTTP2_EXTPRI_URGENCY_LOW`.
+ *
+ * If |ignore_client_signal| is nonzero, server starts to ignore
+ * client priority signals for this stream.
+ *
+ * If
+ * :enum:`nghttp2_settings_id.NGHTTP2_SETTINGS_NO_RFC7540_PRIORITIES`
+ * of value of 1 is not submitted via `nghttp2_submit_settings()`,
+ * this function does nothing and returns 0.
+ *
+ * :enum:`nghttp2_error.NGHTTP2_ERR_NOMEM`
+ *     Out of memory.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_INVALID_STATE`
+ *     The |session| is initialized as client.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_INVALID_ARGUMENT`
+ *     |stream_id| is zero; or a stream denoted by |stream_id| is not
+ *     found.
+ */
+NGHTTP2_EXTERN int nghttp2_session_change_extpri_stream_priority(
+    nghttp2_session *session, int32_t stream_id, const nghttp2_extpri *extpri,
+    int ignore_client_signal);
+
 /**
  * @function
  *
diff --git a/lib/nghttp2_session.c b/lib/nghttp2_session.c
index dc8eb349..134b0efb 100644
--- a/lib/nghttp2_session.c
+++ b/lib/nghttp2_session.c
@@ -4084,6 +4084,7 @@ static int session_end_stream_headers_received(nghttp2_session *session,
   if (session->server && session_enforce_http_messaging(session) &&
       frame->headers.cat == NGHTTP2_HCAT_REQUEST &&
       (stream->flags & NGHTTP2_STREAM_FLAG_NO_RFC7540_PRIORITIES) &&
+      !(stream->flags & NGHTTP2_STREAM_FLAG_IGNORE_CLIENT_PRIORITIES) &&
       (stream->http_flags & NGHTTP2_HTTP_FLAG_PRIORITY)) {
     rv = session_update_stream_priority(session, stream, stream->http_extpri);
     if (rv != 0) {
@@ -5333,6 +5334,9 @@ int nghttp2_session_on_priority_update_received(nghttp2_session *session,
   stream = nghttp2_session_get_stream_raw(session, priority_update->stream_id);
   if (stream) {
     /* Stream already exists. */
+    if (stream->flags & NGHTTP2_STREAM_FLAG_IGNORE_CLIENT_PRIORITIES) {
+      return session_call_on_frame_received(session, frame);
+    }
   } else if (session_detect_idle_stream(session, priority_update->stream_id)) {
     if (session->num_idle_streams + session->num_incoming_streams >=
         session->local_settings.max_concurrent_streams) {
@@ -8375,3 +8379,38 @@ nghttp2_session_get_hd_deflate_dynamic_table_size(nghttp2_session *session) {
 void nghttp2_session_set_user_data(nghttp2_session *session, void *user_data) {
   session->user_data = user_data;
 }
+
+int nghttp2_session_change_extpri_stream_priority(
+    nghttp2_session *session, int32_t stream_id,
+    const nghttp2_extpri *extpri_in, int ignore_client_signal) {
+  nghttp2_stream *stream;
+  nghttp2_extpri extpri = *extpri_in;
+
+  if (!session->server) {
+    return NGHTTP2_ERR_INVALID_STATE;
+  }
+
+  if (session->pending_no_rfc7540_priorities != 1) {
+    return 0;
+  }
+
+  if (stream_id == 0) {
+    return NGHTTP2_ERR_INVALID_ARGUMENT;
+  }
+
+  stream = nghttp2_session_get_stream_raw(session, stream_id);
+  if (!stream) {
+    return NGHTTP2_ERR_INVALID_ARGUMENT;
+  }
+
+  if (extpri.urgency > NGHTTP2_EXTPRI_URGENCY_LOW) {
+    extpri.urgency = NGHTTP2_EXTPRI_URGENCY_LOW;
+  }
+
+  if (ignore_client_signal) {
+    stream->flags |= NGHTTP2_STREAM_FLAG_IGNORE_CLIENT_PRIORITIES;
+  }
+
+  return session_update_stream_priority(session, stream,
+                                        nghttp2_extpri_to_uint8(&extpri));
+}
diff --git a/lib/nghttp2_stream.h b/lib/nghttp2_stream.h
index 4f5585e8..0ec77bf0 100644
--- a/lib/nghttp2_stream.h
+++ b/lib/nghttp2_stream.h
@@ -94,6 +94,8 @@ typedef enum {
   /* Indicates that this stream is not subject to RFC7540
      priorities scheme. */
   NGHTTP2_STREAM_FLAG_NO_RFC7540_PRIORITIES = 0x10,
+  /* Ignore client RFC 9218 priority signal. */
+  NGHTTP2_STREAM_FLAG_IGNORE_CLIENT_PRIORITIES = 0x20,
 } nghttp2_stream_flag;
 
 /* HTTP related flags to enforce HTTP semantics */
diff --git a/tests/main.c b/tests/main.c
index 92ce6679..ed26a80a 100644
--- a/tests/main.c
+++ b/tests/main.c
@@ -317,6 +317,8 @@ int main(void) {
       !CU_add_test(pSuite, "session_flooding", test_nghttp2_session_flooding) ||
       !CU_add_test(pSuite, "session_change_stream_priority",
                    test_nghttp2_session_change_stream_priority) ||
+      !CU_add_test(pSuite, "session_change_extpri_stream_priority",
+                   test_nghttp2_session_change_extpri_stream_priority) ||
       !CU_add_test(pSuite, "session_create_idle_stream",
                    test_nghttp2_session_create_idle_stream) ||
       !CU_add_test(pSuite, "session_repeated_priority_change",
diff --git a/tests/nghttp2_session_test.c b/tests/nghttp2_session_test.c
index cf5a775d..be13f5f4 100644
--- a/tests/nghttp2_session_test.c
+++ b/tests/nghttp2_session_test.c
@@ -10698,6 +10698,84 @@ void test_nghttp2_session_change_stream_priority(void) {
   nghttp2_session_del(session);
 }
 
+void test_nghttp2_session_change_extpri_stream_priority(void) {
+  nghttp2_session *session;
+  nghttp2_session_callbacks callbacks;
+  nghttp2_bufs bufs;
+  nghttp2_buf *buf;
+  ssize_t rv;
+  nghttp2_option *option;
+  nghttp2_extension frame;
+  nghttp2_ext_priority_update priority_update;
+  nghttp2_extpri extpri;
+  nghttp2_stream *stream;
+  static const uint8_t field_value[] = "u=2";
+
+  memset(&callbacks, 0, sizeof(nghttp2_session_callbacks));
+
+  frame_pack_bufs_init(&bufs);
+
+  nghttp2_option_new(&option);
+  nghttp2_option_set_builtin_recv_extension_type(option,
+                                                 NGHTTP2_PRIORITY_UPDATE);
+
+  nghttp2_session_server_new2(&session, &callbacks, NULL, option);
+
+  session->pending_no_rfc7540_priorities = 1;
+
+  open_recv_stream(session, 1);
+
+  extpri.urgency = NGHTTP2_EXTPRI_URGENCY_LOW + 1;
+  extpri.inc = 1;
+
+  rv = nghttp2_session_change_extpri_stream_priority(
+      session, 1, &extpri, /* ignore_client_signal = */ 0);
+
+  CU_ASSERT(0 == rv);
+
+  stream = nghttp2_session_get_stream(session, 1);
+
+  CU_ASSERT(NGHTTP2_EXTPRI_URGENCY_LOW ==
+            nghttp2_extpri_uint8_urgency(stream->extpri));
+  CU_ASSERT(1 == nghttp2_extpri_uint8_inc(stream->extpri));
+
+  /* Client can still update stream priority. */
+  frame.payload = &priority_update;
+  nghttp2_frame_priority_update_init(&frame, 1, (uint8_t *)field_value,
+                                     sizeof(field_value) - 1);
+  nghttp2_frame_pack_priority_update(&bufs, &frame);
+
+  buf = &bufs.head->buf;
+  rv = nghttp2_session_mem_recv(session, buf->pos, nghttp2_buf_len(buf));
+
+  CU_ASSERT((ssize_t)nghttp2_buf_len(buf) == rv);
+  CU_ASSERT(2 == stream->extpri);
+
+  /* Start to ignore client priority signal for this stream. */
+  rv = nghttp2_session_change_extpri_stream_priority(
+      session, 1, &extpri, /* ignore_client_signal = */ 1);
+
+  CU_ASSERT(0 == rv);
+
+  stream = nghttp2_session_get_stream(session, 1);
+
+  CU_ASSERT(NGHTTP2_EXTPRI_URGENCY_LOW ==
+            nghttp2_extpri_uint8_urgency(stream->extpri));
+  CU_ASSERT(1 == nghttp2_extpri_uint8_inc(stream->extpri));
+
+  buf = &bufs.head->buf;
+  rv = nghttp2_session_mem_recv(session, buf->pos, nghttp2_buf_len(buf));
+
+  CU_ASSERT((ssize_t)nghttp2_buf_len(buf) == rv);
+  CU_ASSERT(NGHTTP2_EXTPRI_URGENCY_LOW ==
+            nghttp2_extpri_uint8_urgency(stream->extpri));
+  CU_ASSERT(1 == nghttp2_extpri_uint8_inc(stream->extpri));
+
+  nghttp2_session_del(session);
+  nghttp2_option_del(option);
+  nghttp2_bufs_free(&bufs);
+}
+
 void test_nghttp2_session_create_idle_stream(void) {
   nghttp2_session *session;
   nghttp2_session_callbacks callbacks;
diff --git a/tests/nghttp2_session_test.h b/tests/nghttp2_session_test.h
index a46d0220..e2710e34 100644
--- a/tests/nghttp2_session_test.h
+++ b/tests/nghttp2_session_test.h
@@ -155,6 +155,7 @@ void test_nghttp2_session_defer_then_close(void);
 void test_nghttp2_session_detach_item_from_closed_stream(void);
 void test_nghttp2_session_flooding(void);
 void test_nghttp2_session_change_stream_priority(void);
+void test_nghttp2_session_change_extpri_stream_priority(void);
 void test_nghttp2_session_create_idle_stream(void);
 void test_nghttp2_session_repeated_priority_change(void);
 void test_nghttp2_session_repeated_priority_submission(void);