diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 432802b..553016a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -3,7 +3,7 @@ on:
   - pull_request
 jobs:
   test:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     name: OTP ${{matrix.otp}} / Elixir ${{matrix.elixir}}
     strategy:
       fail-fast: false
diff --git a/lib/exq_scheduler/serializer.ex b/lib/exq_scheduler/serializer.ex
index 71e1661..4f9f864 100644
--- a/lib/exq_scheduler/serializer.ex
+++ b/lib/exq_scheduler/serializer.ex
@@ -1,5 +1,6 @@
 defmodule ExqScheduler.Serializer do
-  @serializer Application.fetch_env!(:exq_scheduler, :storage)[:json_serializer] || Poison
+  @storage Application.get_env(:exq_scheduler, :storage, [])
+  @serializer Keyword.get(@storage, :json_serializer, Poison)
 
   def encode!(object, opts \\ []) do
     @serializer.encode!(object, opts)