diff --git a/lib/rails_erd/domain/relationship.rb b/lib/rails_erd/domain/relationship.rb
index <HASH>..<HASH> 100644
--- a/lib/rails_erd/domain/relationship.rb
+++ b/lib/rails_erd/domain/relationship.rb
@@ -190,7 +190,7 @@ module RailsERD
       end
 
       def foreign_key_required?(association)
-        if association.belongs_to?
+        if !association.active_record.abstract_class? and association.belongs_to?
           column = association.active_record.columns_hash[association.send(Domain.foreign_key_method_name)] and !column.null
         end
       end
Checks that a model is not abstract before all 

Fixes #<I>.