diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 10982d50c9784478533ac56039c80886cfd62855..e16093bd02a6f8c49b6204e261ac8057cfac5ccb 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1,10 +1,10 @@
 stages:
-  - build
+- build
 
 build:
   stage: build
   script:
-    - docker build -t registry.magic-technik.de/gitlab-ci/android .
-    - docker push registry.magic-technik.de/gitlab-ci/android
+  - docker build -t registry.magic-technik.de/gitlab-ci/android .
+  - docker push registry.magic-technik.de/gitlab-ci/android
   tags:
-    - docker
+  - docker
diff --git a/Dockerfile b/Dockerfile
index 1f0dc330d87730be725c2efbb08b28c94d8b1317..77bc32c3c88094a28d16c926d8d2f1d62670a8ee 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -8,7 +8,7 @@
 FROM ubuntu:16.04
 MAINTAINER Jan Grewe <jan@faked.org>
 
-ENV VERSION_SDK_TOOLS "25.1.7"
+ENV VERSION_SDK_TOOLS "25.2.2"
 ENV VERSION_BUILD_TOOLS "24.0.2"
 ENV VERSION_TARGET_SDK "24"
 
@@ -29,7 +29,7 @@ RUN apt-get -qq update && \
       lib32ncurses5 \
       lib32z1 \
       unzip \
-    && rm -rf /tmp/* /var/tmp/* /var/lib/apt/lists/* /var/cache/apt/*
+    && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
 RUN rm -f /etc/ssl/certs/java/cacerts; \
     /var/lib/dpkg/info/ca-certificates-java.postinst configure
@@ -38,4 +38,8 @@ ADD http://dl.google.com/android/repository/tools_r${VERSION_SDK_TOOLS}-linux.zi
 RUN unzip /tools.zip -d /sdk && \
     rm -v /tools.zip
 
+RUN mkdir -p $ANDROID_HOME/licenses/ \
+  && echo "8933bad161af4178b1185d1a37fbf41ea5269c55" > $ANDROID_HOME/licenses/android-sdk-license \
+  && echo "84831b9409646a918e30573bab4c9c91346d8abd" > $ANDROID_HOME/licenses/android-sdk-preview-license
+
 RUN (while [ 1 ]; do sleep 5; echo y; done) | ${ANDROID_HOME}/tools/android update sdk -u -a -t ${SDK_PACKAGES}
diff --git a/README.md b/README.md
new file mode 100644
index 0000000000000000000000000000000000000000..2a8c84f597c05a4bb4ad0bc4f86f1c6f697a0ecd
--- /dev/null
+++ b/README.md
@@ -0,0 +1,28 @@
+# gitlab-ci-android
+This Docker image contains the Android SDK and most common packages necessary for building Android apps in a CI tool like GitLab CI. Make sure your CI environment's caching works as expected, this greatly improves the build time, especially if you use multiple build jobs.
+
+A `.gitlab-ci.yml` with caching of your project's dependencies would look like this:
+
+```
+image: registry.magic-technik.de/gitlab-ci/android
+
+stages:
+- build
+
+before_script:
+- export GRADLE_USER_HOME=$(pwd)/.gradle
+- chmod +x ./gradlew
+
+cache:
+  key: ${CI_PROJECT_ID}
+  paths:
+  - .gradle/
+
+build:
+  stage: build
+  script:
+  - ./gradlew assembleDebug
+  artifacts:
+    paths:
+    - app/build/outputs/apk/app-debug.apk
+```