diff --git a/Dockerfile b/Dockerfile
index c005cc67..87d77f4c 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM ruby:2.3
+FROM ruby:2.3.3
 RUN \
     apt-get update \
     && apt-get install -y --no-install-recommends netcat nodejs \