diff --git a/.circleci/config.yml b/.circleci/config.yml
index 5f02811..14be22f 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -1,7 +1,7 @@
 # Check https://circleci.com/docs/2.0/language-javascript/ for more details
 
 cache_key: &cache_key
-  dependencies-{{ arch }}-{{ checksum "package.json" }}-{{ checksum "esy.lock.json" }}
+  dependencies-v1-{{ arch }}-{{ checksum "package.json" }}-{{ checksum "esy.lock.json" }}
 
 steps: &steps
 - checkout
@@ -25,15 +25,26 @@ steps: &steps
     keys:
     - *cache_key
 
-- run: npm install -g esy@latest
+- run: npm install -g esy@0.3.4
+- run: ls -l $(which esy)
 - run: esy install
 - run: esy build
 
 - save_cache:
     paths:
       - ~/.esy
+      # - ~/.esy/3/i
+      # - ~/.esy/source-tarballs
     key: *cache_key
 
+- run:
+    name: Format
+    command: esy format
+
+- run:
+    name: Check dirty workspace
+    command: git diff --no-ext-diff --quiet --exit-code
+
 - run:
     name: Run esy test
     command: esy test
diff --git a/executable/ReasonServerApp.re b/executable/ReasonServerApp.re
index bccfa17..0afc6dd 100644
--- a/executable/ReasonServerApp.re
+++ b/executable/ReasonServerApp.re
@@ -1,3 +1 @@
-
 ReasonServer.Server.run();
-
diff --git a/package.json b/package.json
index 34e0d80..9c66516 100644
--- a/package.json
+++ b/package.json
@@ -23,7 +23,8 @@
     "test": "esy x TestReasonServer.exe",
     "utop": "dune utop library -- -implicit-bindings",
     "run": "esy x ReasonServerApp.exe",
-    "watch": "watchexec esy"
+    "watch": "watchexec esy",
+    "format": "bash -c 'refmt --in-place library/*.re executable/*.re'"
   },
   "dependencies": {
     "@esy-ocaml/reason": "^3.3.7",