diff --git a/src/gui_gtk_x11.c b/src/gui_gtk_x11.c
index 67ee531..6c97d1a 100644
--- a/src/gui_gtk_x11.c
+++ b/src/gui_gtk_x11.c
@@ -797,8 +797,8 @@
 # if GTK_CHECK_VERSION(3,10,0)
     static gboolean
 scale_factor_event(GtkWidget *widget,
-	           GParamSpec* pspec UNUSED,
-	           gpointer   user_data UNUSED)
+		   GParamSpec* pspec UNUSED,
+		   gpointer   user_data UNUSED)
 {
     if (gui.surface != NULL)
 	cairo_surface_destroy(gui.surface);