diff --git a/lib/rails_admin/adapters/active_record/association.rb b/lib/rails_admin/adapters/active_record/association.rb
index 924afc1274..74e4076e48 100644
--- a/lib/rails_admin/adapters/active_record/association.rb
+++ b/lib/rails_admin/adapters/active_record/association.rb
@@ -39,7 +39,11 @@ def foreign_key
 
         def foreign_key_nullable?
           return if foreign_key.nil? || type != :has_many
-          klass.columns_hash[foreign_key.to_s].null
+          if klass.columns_hash[association.foreign_key.to_s]
+            klass.columns_hash[association.foreign_key.to_s].null
+          else
+            true
+          end
         end
 
         def foreign_type