diff --git a/Dockerfile b/Dockerfile
index 4be5181..16abd9c 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -4,7 +4,7 @@ MAINTAINER friends@niiknow.org
 
 ENV LC_ALL=en_US.UTF-8 LANG=en_US.UTF-8 LANGUAGE=en_US.UTF-8 \
     TERM=xterm container=docker DEBIAN_FRONTEND=noninteractive \
-    NGINX_VERSION=1.13.1-1~xenial_amd64.deb
+    NGINX_VERSION=1.13.3-1~xenial_amd64.deb
 
 ADD ./build/nginx_${NGINX_VERSION} /tmp
 
diff --git a/README.md b/README.md
index b3f21ae..71c3ff0 100644
--- a/README.md
+++ b/README.md
@@ -7,7 +7,7 @@ Features:
 - [x] image crop offset, credit: https://github.com/bobrik/nginx_image_filter
 - [x] /healthcheck endpoint
 - [x] empty gif on other errors: 403, 404, 415, 500, 502, 503, 504
-- [x] convert/force output to another format
+- [x] convert/force output to another format, support formats: bmp, jpg, png, gif, webp
 
 # What does this solve?
 You have a huge repository of images that need dynamic resize and cropping.  Cloudinary can be expensive and redundant if you run your own CDN in front of this microservice.
diff --git a/build/Dockerfile b/build/Dockerfile
index 11d54fd..7af6627 100644
--- a/build/Dockerfile
+++ b/build/Dockerfile
@@ -1,4 +1,4 @@
-FROM hyperknot/baseimage16:1.0.1
+FROM hyperknot/baseimage16:1.0.2
 
 MAINTAINER friends@niiknow.org
 
diff --git a/build/nginx-dbg_1.13.3-1~xenial_amd64.deb b/build/nginx-dbg_1.13.3-1~xenial_amd64.deb
new file mode 100644
index 0000000..afebe4a
Binary files /dev/null and b/build/nginx-dbg_1.13.3-1~xenial_amd64.deb differ
diff --git a/build/nginx_1.13.1-1~xenial_amd64.deb b/build/nginx_1.13.1-1~xenial_amd64.deb
deleted file mode 100644
index 45e52b0..0000000
Binary files a/build/nginx_1.13.1-1~xenial_amd64.deb and /dev/null differ
diff --git a/build/nginx_1.13.3-1~xenial_amd64.deb b/build/nginx_1.13.3-1~xenial_amd64.deb
new file mode 100644
index 0000000..21d5cbd
Binary files /dev/null and b/build/nginx_1.13.3-1~xenial_amd64.deb differ
diff --git a/build/src/ubuntu.sh b/build/src/ubuntu.sh
index d5c258b..5869911 100644
--- a/build/src/ubuntu.sh
+++ b/build/src/ubuntu.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-export NGINX_VERSION=1.13.1
+export NGINX_VERSION=1.13.3
 export NGINX_BUILD_DIR=/usr/src/nginx/nginx-${NGINX_VERSION}
 
 cd /tmp