diff --git a/Dockerfile b/Dockerfile
index 2e07ad2..26f844b 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,7 +1,7 @@
 FROM openjdk:8-jre-alpine
 ENV AOZORA_EPUB3 AozoraEpub3-1.1.0b46.zip
 ENV KINDLEGEN kindlegen_linux_2.6_i386_v2_9.tar.gz
-ENV NAROU_VERSION 3.1.5
+ENV NAROU_VERSION 3.1.9
 WORKDIR /opt/narou
 
 RUN apk --update add ruby ruby-io-console ruby-json wget unzip && rm -rf /var/cache/apk/*
@@ -14,11 +14,14 @@ RUN wget http://kindlegen.s3.amazonaws.com/${KINDLEGEN} && \
     tar zxf ${KINDLEGEN} -C /opt/kindlegen && \
     rm ${KINDLEGEN}
 
+COPY narou-${NAROU_VERSION}.gem .
 RUN apk add --no-cache --virtual .ruby-builddeps build-base libffi-dev ruby-dev && \
     gem install narou -v ${NAROU_VERSION} --no-document && \
     apk del .ruby-builddeps
 
 COPY init.sh /usr/local/bin
 
+WORKDIR /opt/narou/work
+
 ENTRYPOINT ["init.sh"]
 CMD ["narou"]
diff --git a/Makefile b/Makefile
index e9b7ab3..57efac6 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,6 @@
 
-VERSION = v1.4
+RELEASE_VERSION = v1.5
+VERSION = latest
 
 OPTIONS = \
 	--build-arg http_proxy=${http_proxy} \
@@ -10,4 +11,7 @@ OPTIONS = \
 build: FORCE
 	docker build -t jam7/narou-alpine:${VERSION} ${OPTIONS} .
 
+release: FORCE
+	docker build -t jam7/narou-alpine:${RELEASE_VERSION} ${OPTIONS} .
+
 FORCE: