diff --git a/src/backends/meta-monitor-manager.c b/src/backends/meta-monitor-manager.c
index 1ba007cfa..441a9a0d8 100644
--- a/src/backends/meta-monitor-manager.c
+++ b/src/backends/meta-monitor-manager.c
@@ -1261,12 +1261,14 @@ meta_monitor_manager_handle_get_current_state (MetaDBusDisplayConfig *skeleton,
                                                GDBusMethodInvocation *invocation)
 {
   MetaMonitorManager *manager = META_MONITOR_MANAGER (skeleton);
+  MetaSettings *settings = meta_backend_get_settings (manager->backend);
   GVariantBuilder monitors_builder;
   GVariantBuilder logical_monitors_builder;
   GVariantBuilder properties_builder;
   GList *l;
   int i;
   MetaMonitorManagerCapability capabilities;
+  int ui_scaling_factor;
   int max_screen_width, max_screen_height;
 
   g_variant_builder_init (&monitors_builder,
@@ -1444,6 +1446,11 @@ meta_monitor_manager_handle_get_current_state (MetaDBusDisplayConfig *skeleton,
                              g_variant_new_boolean (TRUE));
     }
 
+  ui_scaling_factor = meta_settings_get_ui_scaling_factor (settings);
+  g_variant_builder_add (&properties_builder, "{sv}",
+                         "legacy-ui-scaling-factor",
+                         g_variant_new_int32 (ui_scaling_factor));
+
   if (meta_monitor_manager_get_max_screen_size (manager,
                                                 &max_screen_width,
                                                 &max_screen_height))
diff --git a/src/org.gnome.Mutter.DisplayConfig.xml b/src/org.gnome.Mutter.DisplayConfig.xml
index aab2e0faf..fe8e02294 100644
--- a/src/org.gnome.Mutter.DisplayConfig.xml
+++ b/src/org.gnome.Mutter.DisplayConfig.xml
@@ -394,6 +394,10 @@
 				       always use the same scale. Absence of
 				       this means logical monitor scales can
 				       differ.
+	* "legacy-ui-scaling-factor" (i): The legacy scaling factor traditionally
+				          used to scale X11 clients (commonly
+					  communicated via the
+					  Gdk/WindowScalingFactor XSetting entry).
     -->
     <method name="GetCurrentState">
       <arg name="serial" direction="out" type="u" />