Dependency not getting cached in bitbucket pipeline

[Chain Singh]

image: uber/android-build-environment

pipelines:
  branches:
    operation-secret:
      - step:
          caches:
            - custom
          script:
            - mkdir "${ANDROID_HOME}/licenses" || true
            - export GOOGLE_APPLICATION_CREDENTIALS=$PWD/appengine-backend/src/main/webapp/WEB-INF/village-test.json
            - echo "8933bad161af4178b1185d1a37fbf41ea5269c55" > "${ANDROID_HOME}/licenses/android-sdk-license"
            - mkdir -p dependencies
            - cd core-lib
            - ../gradlew build --gradle-user-home ../dependencies
            - cd ..
            - du -s ./dependencies
definitions:
 caches:
 custom: dependencies

In above bitbucket pipeline, I expect in "dependencies" folder 
relative to clone directory, dependencies getting cached. 
But I do not see updated size in bitbucket caches size. 
In next build, build is again downloading all dependencies.