diff --git a/shell/alt/cc-window.c b/shell/alt/cc-window.c
index b4bff0c6b..f12ea9102 100644
--- a/shell/alt/cc-window.c
+++ b/shell/alt/cc-window.c
@@ -898,6 +898,15 @@ stack_page_notify_cb (GtkStack     *stack,
     }
 }
 
+static void
+sidelist_size_allocate_cb (GtkWidget    *box,
+                           GdkRectangle *allocation,
+                           CcWindow     *self)
+{
+  /* Keep the sidelist and the first headerbar synchronized */
+  gtk_widget_set_size_request (self->header, allocation->width, -1);
+}
+
 /* CcShell implementation */
 static void
 _shell_embed_widget_in_header (CcShell      *shell,
@@ -1197,6 +1206,7 @@ cc_window_class_init (CcWindowClass *klass)
   gtk_widget_class_bind_template_callback (widget_class, gdk_window_set_cb);
   gtk_widget_class_bind_template_callback (widget_class, search_entry_changed_cb);
   gtk_widget_class_bind_template_callback (widget_class, search_entry_key_press_event_cb);
+  gtk_widget_class_bind_template_callback (widget_class, sidelist_size_allocate_cb);
   gtk_widget_class_bind_template_callback (widget_class, stack_page_notify_cb);
   gtk_widget_class_bind_template_callback (widget_class, window_map_event_cb);
 }
diff --git a/shell/window.ui b/shell/window.ui
index a42390bf4..afa8efdf4 100644
--- a/shell/window.ui
+++ b/shell/window.ui
@@ -16,6 +16,7 @@
             <property name="can_focus">False</property>
             <property name="hexpand">False</property>
             <property name="orientation">vertical</property>
+            <signal name="size-allocate" handler="sidelist_size_allocate_cb" object="CcWindow" swapped="no" />
             <child>
               <object class="GtkSearchBar" id="search_bar">
                 <property name="visible">True</property>