1 files changed, 7 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/associations/builder/has_one.rb b/activerecord/lib/active_record/associations/builder/has_one.rb
index 64e9e6b334..a272d3c781 100644
--- a/activerecord/lib/active_record/associations/builder/has_one.rb
+++ b/activerecord/lib/active_record/associations/builder/has_one.rb
@@ -17,5 +17,12 @@ module ActiveRecord::Associations::Builder
     def self.add_destroy_callbacks(model, reflection)
       super unless reflection.options[:through]
     end
+
+    def self.define_validations(model, reflection)
+      super
+      if reflection.options[:required]
+        model.validates_presence_of reflection.name, message: :required
+      end
+    end
   end
 end