diff --git a/Dockerfile b/Dockerfile
index 19090533757..1e60045c019 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,5 +1,5 @@
 FROM node:8.15-alpine as node
-FROM ruby:2.6-alpine3.8
+FROM ruby:2.6-alpine3.9
 
 LABEL maintainer="https://github.com/tootsuite/mastodon" \
       description="Your self-hosted, globally interconnected microblogging community"