diff --git a/docs/Makefile b/docs/Makefile
index b458da2..06fa746 100644
--- a/docs/Makefile
+++ b/docs/Makefile
@@ -21,6 +21,10 @@ install:
 s serve:
 	bundle exec jekyll serve --trace --livereload
 
+define baseurlparam =
+$(if $(BASE_URL),-- --baseurl $(BASE_URL),-- --baseurl "")
+endef
+
 build: version
 	npm run build $(baseurlparam)