diff --git a/dlib/gui_widgets/widgets.cpp b/dlib/gui_widgets/widgets.cpp
index 3aefa66a0..08b3e8de5 100644
--- a/dlib/gui_widgets/widgets.cpp
+++ b/dlib/gui_widgets/widgets.cpp
@@ -2238,6 +2238,7 @@ namespace dlib
         last_selected(0)
     {
         set_vertical_scroll_increment(mfont->height());
+        set_horizontal_scroll_increment(mfont->height());
 
         style.reset(new list_box_style_default());
         enable_events();