diff --git a/src/testdir/Make_os2.mak b/src/testdir/Make_os2.mak
index 08f78cb..9150af7 100644
--- a/src/testdir/Make_os2.mak
+++ b/src/testdir/Make_os2.mak
@@ -42,6 +42,7 @@
 		test_autocmd_option.out \
 		test_autoformat_join.out \
 		test_breakindent.out \
+		test_cdo.out \
 		test_changelist.out \
 		test_charsearch.out \
 		test_close_count.out \