diff --git a/commit-watcher/Dockerfile b/commit-watcher/Dockerfile
index 9b010bd..f2438d0 100644
--- a/commit-watcher/Dockerfile
+++ b/commit-watcher/Dockerfile
@@ -4,7 +4,8 @@ RUN	apk add --no-cache \
 	ca-certificates \
 	libxml2 \
 	libxslt \
-	ruby
+	ruby \
+	ruby-bigdecimal
 
 RUN	set -x \
 	&& apk add --no-cache --virtual .build-deps \
@@ -17,7 +18,7 @@ RUN	set -x \
 	ruby-dev \
 	&& git clone --depth 1 https://github.com/srcclr/commit-watcher.git /usr/src/commit-watcher \
 	&& cd /usr/src/commit-watcher \
-	&& gem install bigdecimal bundler io-console --no-rdoc --no-ri \
+	&& gem install bundler io-console --no-rdoc --no-ri \
 	&& bundle config build.nokogiri --use-system-libraries \
 	&& bundle install \
 	&& apk del .build-deps