diff --git a/FL/Fl_Preferences.H b/FL/Fl_Preferences.H
index f59c255d7..e0cf1ed7c 100644
--- a/FL/Fl_Preferences.H
+++ b/FL/Fl_Preferences.H
@@ -31,6 +31,7 @@
 #ifndef Fl_Preferences_H
 #  define Fl_Preferences_H
 
+#  include <stdio.h>
 #  include "Fl_Export.H"