diff --git a/ci/install-dependencies.sh b/ci/install-dependencies.sh
index 2f61fbb07c..502e518077 100755
--- a/ci/install-dependencies.sh
+++ b/ci/install-dependencies.sh
@@ -166,6 +166,7 @@ sparse)
 Documentation)
 	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
 	;;