diff --git a/libs/gtkmm2ext/gtkapplication_quartz.mm b/libs/gtkmm2ext/gtkapplication_quartz.mm
index c5fb8b12e2..03051849d3 100644
--- a/libs/gtkmm2ext/gtkapplication_quartz.mm
+++ b/libs/gtkmm2ext/gtkapplication_quartz.mm
@@ -1373,7 +1373,7 @@ gtk_application_add_app_menu_item (GtkApplicationMenuGroup *group,
 namespace Gtk {
 	namespace Application {
 		sigc::signal<void,bool> ActivationChanged;
-		sigc::signal<void,const Glib::ustring&> ShouldLoad;
+		sigc::signal<void,const std::string&> ShouldLoad;
 		sigc::signal<void> ShouldQuit;
 	}
 }
@@ -1420,7 +1420,7 @@ namespace Gtk {
 @implementation GtkApplicationDelegate
 -(BOOL) application:(NSApplication*) theApplication openFile:(NSString*) file
 {
-	Glib::ustring utf8_path ([file UTF8String]);
+	std::string utf8_path ([file UTF8String]);
 	Gtkmm2ext::Application::instance()->ShouldLoad (utf8_path);
 	return 1;
 }
diff --git a/libs/gtkmm2ext/gtkmm2ext/application.h b/libs/gtkmm2ext/gtkmm2ext/application.h
index 3fb107b783..d3de5e1c7f 100644
--- a/libs/gtkmm2ext/gtkmm2ext/application.h
+++ b/libs/gtkmm2ext/gtkmm2ext/application.h
@@ -22,6 +22,7 @@
 #ifndef __GTK_APPLICATION_MM_H__
 #define __GTK_APPLICATION_MM_H__
 
+#include <string>
 #include <gtkmm2ext/gtkapplication.h> // for GtkApplicationGroup typedef
 #include <sigc++/signal.h>
 
@@ -30,10 +31,6 @@ namespace Gtk {
 	class MenuShell;
 }
 
-namespace Glib {
-	class ustring;
-}
-
 namespace Gtkmm2ext {
 
 class Application 
@@ -49,7 +46,7 @@ public:
     void                     add_app_menu_item (GtkApplicationMenuGroup*, Gtk::MenuItem*);
 
     sigc::signal<void,bool>                 ActivationChanged;
-    sigc::signal<void,const Glib::ustring&> ShouldLoad;
+    sigc::signal<void,const std::string&>   ShouldLoad;
     sigc::signal<void>                      ShouldQuit;
 
 private: