diff --git a/lib/tapioca/runtime/loader.rb b/lib/tapioca/runtime/loader.rb
index 294f26775..9d584daae 100644
--- a/lib/tapioca/runtime/loader.rb
+++ b/lib/tapioca/runtime/loader.rb
@@ -52,6 +52,8 @@ def require_helper(file)
       def rails_engines
         return [] unless Object.const_defined?("Rails::Engine")
 
+        safe_require("active_support/core_ext/class/subclasses")
+
         # We can use `Class#descendants` here, since we know Rails is loaded
         Object.const_get("Rails::Engine").descendants.reject(&:abstract_railtie?)
       end