diff --git a/runtime/doc/Makefile b/runtime/doc/Makefile
index 57aec4e..0cbe020 100644
--- a/runtime/doc/Makefile
+++ b/runtime/doc/Makefile
@@ -323,7 +323,7 @@
 # Use Vim to generate the tags file.  Can only be used when Vim has been
 # compiled and installed.  Supports multiple languages.
 vimtags: $(DOCS)
-	@if test -x $(VIMEXE); then $(VIMEXE) -eX -u doctags.vim; \
+	@if test -x $(VIMEXE); then $(VIMEXE) --clean -eX -u doctags.vim; \
 		else echo "vim executable $(VIMEXE) not found"; fi
 
 # Use "doctags" to generate the tags file.  Only works for English!