diff --git a/.circleci/config.yml b/.circleci/config.yml
index 9d4b5d6d62..20492e262d 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -47,6 +47,8 @@ jobs:
     docker:
       - image: elixir:<< parameters.elixir_version >>
       - image: cimg/postgres:15.3
+    environment:
+      ERL_FLAGS: +S 4:4
 
     steps:
       - checkout
@@ -55,7 +57,11 @@ jobs:
 
       - run:
           name: "Save Elixir and Erlang version for PLT caching"
-          command: echo "$ELIXIR_VERSION $OTP_VERSION" > .elixir_otp_version
+          command: echo "$ELIXIR_VERSION $OTP_VERSION" | tee .elixir_otp_version
+
+      - run:
+          name: "Introspect schedulers"
+          command: elixir -v
 
       - restore_cache:
           keys:
diff --git a/mix.exs b/mix.exs
index cfdae2f905..99ae6f1ec7 100644
--- a/mix.exs
+++ b/mix.exs
@@ -8,7 +8,7 @@ defmodule Lightning.MixProject do
       elixir: "~> 1.15",
       elixirc_paths: elixirc_paths(Mix.env()),
       elixirc_options: [
-        warnings_as_errors: false
+        warnings_as_errors: true
       ],
       start_permanent: Mix.env() == :prod,
       aliases: aliases(),
diff --git a/test/test_helper.exs b/test/test_helper.exs
index dcf7f5817d..a9bff4852d 100644
--- a/test/test_helper.exs
+++ b/test/test_helper.exs
@@ -1,4 +1,4 @@
-Code.put_compiler_option(:warnings_as_errors, false)
+Code.put_compiler_option(:warnings_as_errors, true)
 # Report which tests are synchronous
 # Rexbug.start("ExUnit.Server.add_sync_module/_")
 Mox.defmock(Lightning.Tesla.Mock, for: Tesla.Adapter)