fix up extraction procedures
diff --git a/unix/mkfile.mk b/unix/mkfile.mk
index 09d064d..17fd970 100644
--- a/unix/mkfile.mk
+++ b/unix/mkfile.mk
@@ -39,5 +39,5 @@
 NOTICE: ../NOTICE.mk
 	cp $prereq $target
 
-sys.h: $PLAN9/src/cmd/mk/sys.h.std
+sys.h: $PLAN9/src/cmd/mk/sys.std.h
 	cp $prereq $target