diff --git a/Dockerfile b/Dockerfile
index f64ad1e..90376d4 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -5,6 +5,7 @@ MAINTAINER Ryan Davis
 WORKDIR /usr/src/app
 
 RUN gem install --silent hoe minitest rake && \
+    gem install ruby_parser --version 3.13.1 &&  \
     gem install --silent flog -N -v "~> 4.6" # currently 4.6.4
 
 RUN adduser -u 9000 -D -h /usr/src/app -s /bin/false app