diff --git a/src/gui/gsc_info_window.cpp b/src/gui/gsc_info_window.cpp
index f9eada7..06c617b 100644
--- a/src/gui/gsc_info_window.cpp
+++ b/src/gui/gsc_info_window.cpp
@@ -35,7 +35,7 @@ Copyright:
 #include "gsc_info_window.h"
 #include "gsc_executor_error_dialog.h"
 #include "gsc_startup_settings.h"
-#include "gsc_init.h"  // app_get_windows_fractional_scaling_percent()
+#include "gsc_init.h"  // app_apply_fractional_scaling_to_default_size()
 
 
 
diff --git a/src/gui/gsc_init.cpp b/src/gui/gsc_init.cpp
index a7533f2..2f822bc 100644
--- a/src/gui/gsc_init.cpp
+++ b/src/gui/gsc_init.cpp
@@ -119,8 +119,9 @@ void app_apply_fractional_scaling_to_default_size(Gtk::Window* window, int confi
 		int glade_w = 0, glade_h = 0;
 		window->get_default_size(glade_w, glade_h);
 		if (glade_w > 0 && glade_h > 0) {
-			size_w = static_cast<int>(glade_w * (1.0 + fraction_percent / 100.0));
-			size_h = static_cast<int>(glade_h * (1.0 + fraction_percent / 100.0));
+			const double scale_factor = 1.0 + static_cast<double>(fraction_percent) / 100.0;
+			size_w = static_cast<int>(std::lround(glade_w * scale_factor));
+			size_h = static_cast<int>(std::lround(glade_h * scale_factor));
 		}
 	}
 
diff --git a/src/gui/gsc_init.h b/src/gui/gsc_init.h
index 2b9e0b5..585aa5b 100644
--- a/src/gui/gsc_init.h
+++ b/src/gui/gsc_init.h
@@ -15,6 +15,11 @@ Copyright:
 #include <string>
 
 
+namespace Gtk {
+	class Window;
+}
+
+
 /// Initialize the application and run the main loop
 bool app_init_and_loop(int& argc, char**& argv);
 
diff --git a/src/gui/gsc_text_window.h b/src/gui/gsc_text_window.h
index 6fde22f..f45cfa2 100644
--- a/src/gui/gsc_text_window.h
+++ b/src/gui/gsc_text_window.h
@@ -24,7 +24,7 @@ Copyright:
 
 #include "applib/app_builder_widget.h"
 #include "applib/app_gtkmm_tools.h"
-#include "gsc_init.h"  // app_get_windows_fractional_scaling_percent()
+#include "gsc_init.h"  // app_apply_fractional_scaling_to_default_size()