diff --git a/ci/install-dependencies.sh b/ci/install-dependencies.sh
index 10c3530d1a..2f61fbb07c 100755
--- a/ci/install-dependencies.sh
+++ b/ci/install-dependencies.sh
@@ -164,9 +164,8 @@ sparse)
 		libexpat-dev gettext zlib1g-dev sparse
 	;;
 Documentation)
-	sudo apt-get -q -y install asciidoc xmlto docbook-xsl-ns make
+	sudo apt-get -q -y install asciidoc xmlto docbook-xsl-ns make ruby
 
-	test -n "$ALREADY_HAVE_ASCIIDOCTOR" ||
 	sudo gem install --version 1.5.8 asciidoctor
 	sudo gem install concurrent-ruby
 	;;