diff --git a/.circleci/config.yml b/.circleci/config.yml
index 6e587db7b2a8..b18b668cb784 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -40,20 +40,14 @@ jobs:
     steps: *ci_steps
 
   test_alpine:
-    docker:
-    - image: jrei/crystal-alpine:latest
+    machine: true
     environment:
       <<: *env
       TRAVIS_OS_NAME: linux
       ARCH: x86_64
       ARCH_CMD: linux64
-    steps:
-    - checkout
-    - run: echo 'export CURRENT_TAG="$CIRCLE_TAG"' >> $BASH_ENV
-    - run: bin/ci prepare_build
-    - run: make std_spec clean threads=1
-    - run: make crystal std_spec compiler_spec docs threads=1
-    - run: find samples -name "*.cr" | xargs -L 1 ./bin/crystal build --no-codegen
+      DOCKER_TEST_IMAGE: jrei/crystal-alpine:latest
+    steps: *ci_steps
 
   test_darwin:
     macos:
diff --git a/bin/ci b/bin/ci
index 3559ddbe5825..e060d7551570 100755
--- a/bin/ci
+++ b/bin/ci
@@ -118,10 +118,10 @@ with_build_env() {
 
   case $ARCH in
     x86_64)
-      export DOCKER_TEST_IMAGE="$DOCKER_TEST_PREFIX-build"
+      export DOCKER_TEST_IMAGE="${DOCKER_TEST_IMAGE:=DOCKER_TEST_PREFIX-build}"
       ;;
     i386)
-      export DOCKER_TEST_IMAGE="$DOCKER_TEST_PREFIX-i386-build"
+      export DOCKER_TEST_IMAGE="${DOCKER_TEST_IMAGE:=DOCKER_TEST_PREFIX-i386-build}"
       ;;
   esac