diff --git a/6502/C64/src/v4th-x16e.fth b/6502/C64/src/v4th-x16e.fth
index 8843694..907f686 100644
--- a/6502/C64/src/v4th-x16e.fth
+++ b/6502/C64/src/v4th-x16e.fth
@@ -18,6 +18,7 @@ include vf-head-x16.fth
 include vf-cbm-core.fth
 include vf-sys-x16.fth
 include vf-cbm-file.fth
+include vf-cbm-dos.fth
 include vf-x16edit.fth
 include vf-finalize.fth
   9f00 ' limit >body !  9b00 s0 !  9f00 r0 !