diff -Nru gnome-control-center-3.38.5/debian/changelog gnome-control-center-3.38.5/debian/changelog
--- gnome-control-center-3.38.5/debian/changelog	2021-03-23 15:54:54.000000000 +0800
+++ gnome-control-center-3.38.5/debian/changelog	2021-08-03 16:40:06.000000000 +0800
@@ -1,3 +1,11 @@
+gnome-control-center (1:3.38.5-1ubuntu2) hirsute; urgency=medium
+
+  * d/p/0033-Fix-volume-adjustment-failure-on-volume-slider.patch
+    Can't adjust the output volume via volume-slider after changing
+    the current output-device. (LP: #1938747)
+
+ -- Hui Wang <hui.wang@canonical.com>  Tue, 03 Aug 2021 16:40:06 +0800
+
 gnome-control-center (1:3.38.5-1ubuntu1) hirsute; urgency=medium
 
   * New bugfix update based on Debian
diff -Nru gnome-control-center-3.38.5/debian/patches/0033-Fix-volume-adjustment-failure-on-volume-slider.patch gnome-control-center-3.38.5/debian/patches/0033-Fix-volume-adjustment-failure-on-volume-slider.patch
--- gnome-control-center-3.38.5/debian/patches/0033-Fix-volume-adjustment-failure-on-volume-slider.patch	1970-01-01 08:00:00.000000000 +0800
+++ gnome-control-center-3.38.5/debian/patches/0033-Fix-volume-adjustment-failure-on-volume-slider.patch	2021-08-03 16:38:21.000000000 +0800
@@ -0,0 +1,138 @@
+Index: gnome-control-center-40.0/panels/sound/cc-sound-panel.c
+===================================================================
+--- gnome-control-center-40.0.orig/panels/sound/cc-sound-panel.c
++++ gnome-control-center-40.0/panels/sound/cc-sound-panel.c
+@@ -96,18 +96,12 @@ allow_amplified_changed_cb (CcSoundPanel
+ }
+ 
+ static void
+-output_device_changed_cb (CcSoundPanel *self)
++set_output_stream (CcSoundPanel   *self,
++                   GvcMixerStream *stream)
+ {
+-  GvcMixerUIDevice *device;
+-  GvcMixerStream *stream = NULL;
+   GvcChannelMap *map = NULL;
+   gboolean can_fade = FALSE, has_lfe = FALSE;
+ 
+-  device = cc_device_combo_box_get_device (self->output_device_combo_box);
+-
+-  if (device != NULL)
+-    stream = gvc_mixer_control_get_stream_from_device (self->mixer_control, device);
+-
+   cc_volume_slider_set_stream (self->output_volume_slider, stream, CC_STREAM_TYPE_OUTPUT);
+   cc_volume_slider_set_stream (self->output_volume_slider_ubuntu, stream, CC_STREAM_TYPE_OUTPUT);
+   cc_level_bar_set_stream (self->output_level_bar, stream, CC_STREAM_TYPE_OUTPUT);
+@@ -124,12 +118,34 @@ output_device_changed_cb (CcSoundPanel *
+ 
+   gtk_widget_set_visible (GTK_WIDGET (self->fade_row), can_fade);
+   gtk_widget_set_visible (GTK_WIDGET (self->subwoofer_row), has_lfe);
++}
++
++static void
++output_device_changed_cb (CcSoundPanel *self)
++{
++  GvcMixerUIDevice *device;
++  GvcMixerStream *stream = NULL;
++
++  device = cc_device_combo_box_get_device (self->output_device_combo_box);
++
++  if (device != NULL)
++    stream = gvc_mixer_control_get_stream_from_device (self->mixer_control, device);
++
++  set_output_stream (self, stream);
+ 
+   if (device != NULL)
+     gvc_mixer_control_change_output (self->mixer_control, device);
+ }
+ 
+ static void
++set_input_stream (CcSoundPanel   *self,
++                  GvcMixerStream *stream)
++{
++  cc_volume_slider_set_stream (self->input_volume_slider, stream, CC_STREAM_TYPE_INPUT);
++  cc_level_bar_set_stream (self->input_level_bar, stream, CC_STREAM_TYPE_INPUT);
++}
++
++static void
+ input_device_changed_cb (CcSoundPanel *self)
+ {
+   GvcMixerUIDevice *device;
+@@ -140,8 +156,7 @@ input_device_changed_cb (CcSoundPanel *s
+   if (device != NULL)
+     stream = gvc_mixer_control_get_stream_from_device (self->mixer_control, device);
+ 
+-  cc_volume_slider_set_stream (self->input_volume_slider, stream, CC_STREAM_TYPE_INPUT);
+-  cc_level_bar_set_stream (self->input_level_bar, stream, CC_STREAM_TYPE_INPUT);
++  set_input_stream (self, stream);
+ 
+   if (device != NULL)
+     gvc_mixer_control_change_input (self->mixer_control, device);
+@@ -153,12 +168,18 @@ output_device_update_cb (CcSoundPanel *s
+ {
+   GvcMixerUIDevice *device;
+   gboolean has_multi_profiles;
++  GvcMixerStream *stream = NULL;
+ 
+   device = cc_device_combo_box_get_device (self->output_device_combo_box);
+   cc_profile_combo_box_set_device (self->output_profile_combo_box, self->mixer_control, device);
+   has_multi_profiles = (cc_profile_combo_box_get_profile_count (self->output_profile_combo_box) > 1);
+   gtk_widget_set_visible (GTK_WIDGET (self->output_profile_row),
+                           has_multi_profiles);
++
++  if (cc_volume_slider_get_stream (self->output_volume_slider) == NULL)
++    stream = gvc_mixer_control_get_stream_from_device (self->mixer_control, device);
++  if (stream != NULL)
++    set_output_stream (self, stream);
+ }
+ 
+ static void
+@@ -167,12 +188,18 @@ input_device_update_cb (CcSoundPanel *se
+ {
+   GvcMixerUIDevice *device;
+   gboolean has_multi_profiles;
++  GvcMixerStream *stream = NULL;
+ 
+   device = cc_device_combo_box_get_device (self->input_device_combo_box);
+   cc_profile_combo_box_set_device (self->input_profile_combo_box, self->mixer_control, device);
+   has_multi_profiles = (cc_profile_combo_box_get_profile_count (self->input_profile_combo_box) > 1);
+   gtk_widget_set_visible (GTK_WIDGET (self->input_profile_row),
+                           has_multi_profiles);
++
++  if (cc_volume_slider_get_stream (self->input_volume_slider) == NULL)
++    stream = gvc_mixer_control_get_stream_from_device (self->mixer_control, device);
++  if (stream != NULL)
++    set_input_stream (self, stream);
+ }
+ 
+ static void
+Index: gnome-control-center-40.0/panels/sound/cc-volume-slider.c
+===================================================================
+--- gnome-control-center-40.0.orig/panels/sound/cc-volume-slider.c
++++ gnome-control-center-40.0/panels/sound/cc-volume-slider.c
+@@ -247,6 +247,14 @@ cc_volume_slider_set_stream (CcVolumeSli
+     }
+ }
+ 
++GvcMixerStream *
++cc_volume_slider_get_stream (CcVolumeSlider *self)
++{
++  g_return_val_if_fail (CC_IS_VOLUME_SLIDER (self), NULL);
++
++  return self->stream;
++}
++
+ void
+ cc_volume_slider_set_is_amplified (CcVolumeSlider *self,
+                                    gboolean        is_amplified)
+Index: gnome-control-center-40.0/panels/sound/cc-volume-slider.h
+===================================================================
+--- gnome-control-center-40.0.orig/panels/sound/cc-volume-slider.h
++++ gnome-control-center-40.0/panels/sound/cc-volume-slider.h
+@@ -40,4 +40,6 @@ void cc_volume_slider_set_stream
+ void cc_volume_slider_set_is_amplified  (CcVolumeSlider  *slider,
+                                          gboolean         is_amplified);
+ 
++GvcMixerStream *cc_volume_slider_get_stream (CcVolumeSlider *slider);
++
+ G_END_DECLS
diff -Nru gnome-control-center-3.38.5/debian/patches/series gnome-control-center-3.38.5/debian/patches/series
--- gnome-control-center-3.38.5/debian/patches/series	2021-03-23 15:54:54.000000000 +0800
+++ gnome-control-center-3.38.5/debian/patches/series	2021-08-03 16:38:56.000000000 +0800
@@ -32,3 +32,4 @@
 0027-window-Stop-using-HdyLeaflet.patch
 0030-temporarily-revert-alt-char-key.patch
 0032-online-accounts-maybe-leak-a-reference-to-the-panel.patch
+0033-Fix-volume-adjustment-failure-on-volume-slider.patch