diff --git a/src/testdir/Make_dos.mak b/src/testdir/Make_dos.mak
index 1a98ebb..406d56a 100644
--- a/src/testdir/Make_dos.mak
+++ b/src/testdir/Make_dos.mak
@@ -130,4 +130,4 @@
 	@del vimcmd
 
 opt_test.vim: ../option.c gen_opt_test.vim
-	$(VIMPROG) -u gen_opt_test.vim --noplugin --not-a-term
+	$(VIMPROG) -u gen_opt_test.vim --noplugin --not-a-term ../option.c