diff --git a/libs/ardour/ardour/ardour.h b/libs/ardour/ardour/ardour.h
index 182435a5ef..1f999c092e 100644
--- a/libs/ardour/ardour/ardour.h
+++ b/libs/ardour/ardour/ardour.h
@@ -57,6 +57,7 @@ namespace ARDOUR {
 	extern LIBARDOUR_API PBD::Signal0<void> GUIIdle;
 	extern LIBARDOUR_API PBD::Signal3<bool,std::string,std::string,int> CopyConfigurationFiles;
 	extern LIBARDOUR_API std::map<std::string, bool> reserved_io_names;
+	extern LIBARDOUR_API float ui_scale_factor;
 
 	/**
 	 * @param try_optimization true to enable hardware optimized routines
@@ -85,6 +86,8 @@ namespace ARDOUR {
 	LIBARDOUR_API void setup_fpu ();
 	LIBARDOUR_API std::vector<SyncSource> get_available_sync_options();
 
+	LIBARDOUR_API void set_global_ui_scale_factor (float s);
+
 	/* the @param ui_handler will be called if there are old configuration
 	 * files to be copied. It should (probably) ask the user about the
 	 * action, and return true or false depending on whether or not the
diff --git a/libs/ardour/globals.cc b/libs/ardour/globals.cc
index 54252c2b39..a81d6760f7 100644
--- a/libs/ardour/globals.cc
+++ b/libs/ardour/globals.cc
@@ -162,10 +162,13 @@ PBD::Signal3<bool, std::string, std::string, int>  ARDOUR::CopyConfigurationFile
 
 std::map<std::string, bool> ARDOUR::reserved_io_names;
 
+float ARDOUR::ui_scale_factor = 1.0;
+
 static bool have_old_configuration_files = false;
 static bool running_from_gui             = false;
 static int  cpu_dma_latency_fd           = -1;
 
+
 namespace ARDOUR {
 extern void setup_enum_writer ();
 }
@@ -763,6 +766,10 @@ ARDOUR::no_auto_connect ()
 	return getenv ("ARDOUR_NO_AUTOCONNECT") != 0;
 }
 
+void ARDOUR::set_global_ui_scale_factor (float s) {
+	ui_scale_factor = s;
+}
+
 void
 ARDOUR::setup_fpu ()
 {