diff --git a/activerecord/lib/active_record/associations/association_proxy.rb b/activerecord/lib/active_record/associations/association_proxy.rb
index 1f08ef599e480..c8d72c9f2559f 100644
--- a/activerecord/lib/active_record/associations/association_proxy.rb
+++ b/activerecord/lib/active_record/associations/association_proxy.rb
@@ -8,7 +8,7 @@ def initialize(owner, association_name, association_class_name, association_clas
         @owner = owner
         @options = options
         @association_name = association_name
-        @association_class = eval(association_class_name, __FILE__, __LINE__)
+        @association_class = eval(association_class_name, nil, __FILE__, __LINE__)
         @association_class_primary_key_name = association_class_primary_key_name
 
         reset