--- ./a/FL/Makefile	2014-04-24 20:08:14.000000000 +0200
+++ ./b/FL/Makefile	2014-04-24 22:22:29.000000000 +0200
@@ -40,7 +40,7 @@
 	$(LN) Fl_File_Chooser.H $(DESTDIR)$(includedir)/FL/fl_file_chooser.H
 	$(RM) $(DESTDIR)$(includedir)/FL/fl_file_chooser.h
 	$(LN) Fl_File_Chooser.H $(DESTDIR)$(includedir)/FL/fl_file_chooser.h
-	$(RM) $(DESTDIR)$(includedir)/Fl
+	$(RM) -Rf $(DESTDIR)$(includedir)/Fl
 	$(LN) FL $(DESTDIR)$(includedir)/Fl
 
 uninstall: