Include the --dir argument in the help text.
diff --git a/Doc/tools/mkhowto b/Doc/tools/mkhowto
index d2ff646..4fe97fb 100755
--- a/Doc/tools/mkhowto
+++ b/Doc/tools/mkhowto
@@ -13,6 +13,7 @@
HTML options:
--address, -a Specify an address for page footers.
+ --dir Specify the directory for HTML output.
--link Specify the number of levels to include on each page.
--split, -s Specify a section level for page splitting, default: %(max_split_depth)s.
--iconserver, -i Specify location of icons (default: ./).