diff --git a/core/lib/spree/core/engine.rb b/core/lib/spree/core/engine.rb
index 184b1a7fe8e..8cf1634c3f3 100644
--- a/core/lib/spree/core/engine.rb
+++ b/core/lib/spree/core/engine.rb
@@ -55,18 +55,16 @@ class Engine < ::Rails::Engine
         end
       end
 
-      config.after_initialize do
+      ActiveSupport.on_load(:action_mailer) do
         # Load in mailer previews for apps to use in development.
         # We need to make sure we call `Preview.all` before requiring our
         # previews, otherwise any previews the app attempts to add need to be
         # manually required.
-        if Rails.env.development? || Rails.env.test?
-          ActionMailer::Preview.all
 
-          Dir[root.join("lib/spree/mailer_previews/**/*_preview.rb")].each do |file|
-            require_dependency file
-          end
-        end
+        original_preview_path = preview_path
+        solidus_preview_path = Spree::Core::Engine.root.join 'lib/spree/mailer_previews/**/*_preview.rb'
+
+        self.preview_path = "{#{original_preview_path},#{solidus_preview_path}}"
       end
     end
   end