diff --git a/runtime/doc/Makefile b/runtime/doc/Makefile
index e278933..0f142a3 100644
--- a/runtime/doc/Makefile
+++ b/runtime/doc/Makefile
@@ -142,7 +142,9 @@
 	touch $@
 
 pi_netrw.txt: ../pack/dist/opt/netrw/doc/netrw.txt
-	cp ../pack/dist/opt/netrw/doc/netrw.txt $@
+	cp ../pack/dist/opt/netrw/doc/netrw.txt $@.tmp
+	sed -e '1s/\(.*\)/\0	*pi_netrw.txt*/' $@.tmp > $@ && \
+	rm -f $@.tmp
 
 vietnamese.txt:
 	touch $@