diff --git a/fkreplace/__init__.py b/fkreplace/__init__.py
index 7494cc3..7f0feda 100644
--- a/fkreplace/__init__.py
+++ b/fkreplace/__init__.py
@@ -11,7 +11,7 @@ class OneToOneConflict(MergeException):
 
 ERROR = 0
 KEEP = 1
-UPDATE = 2
+DELETE = 2
 
 
 def merge(from_obj, to_obj, one_to_one_conflict=ERROR):
@@ -32,8 +32,18 @@ def merge(from_obj, to_obj, one_to_one_conflict=ERROR):
             try:
                 field = getattr(from_obj, accessor_name)
                 try:
-                    to_obj_field = getattr(to_obj, accessor_name)
-                    raise OneToOneConflict("both fields have an attribute set for {}".format(accessor_name))
+                    to_field = getattr(to_obj, accessor_name)
+                    if one_to_one_conflict == KEEP:
+                        pass    # do nothing
+                    elif one_to_one_conflict == DELETE:
+                        # if null:
+                        #   setattr(to_field, varname, None)
+                        #   to_field.save()
+                        to_field.delete()
+                        setattr(field, varname, to_obj)
+                        field.save()
+                    else:
+                        raise OneToOneConflict("both fields have an attribute set for {}".format(accessor_name))
                 except ObjectDoesNotExist:
                     # doesn't exist, safe to overwrite
                     setattr(field, varname, to_obj)
diff --git a/tests/tests.py b/tests/tests.py
index 3e2499c..faa045d 100644
--- a/tests/tests.py
+++ b/tests/tests.py
@@ -1,6 +1,6 @@
 from django.test import TestCase
 from .models import Person, Number, SSN, Group
-from fkreplace import merge, OneToOneConflict
+from fkreplace import merge, OneToOneConflict, KEEP, DELETE
 
 class MergeTests(TestCase):
     def setUp(self):
@@ -43,14 +43,31 @@ class MergeTests(TestCase):
         assert Person.objects.get(pk=self.b.pk).ssn.number == '1'
         assert SSN.objects.count() == 1
 
-    # TODO: test one2one when there's a conflict
     def test_one2one_conflict(self):
         SSN.objects.create(person=self.a, number='1')
-        SSN.objects.create(person=self.b, number='1')
+        SSN.objects.create(person=self.b, number='2')
 
         with self.assertRaises(OneToOneConflict):
             merge(self.a, self.b)
 
+    def test_one2one_conflict_keep(self):
+        SSN.objects.create(person=self.a, number='1')
+        SSN.objects.create(person=self.b, number='2')
+
+        merge(self.a, self.b, KEEP)
+
+        assert Person.objects.get(pk=self.a.pk).ssn.number == '1'
+        assert Person.objects.get(pk=self.b.pk).ssn.number == '2'
+
+    def test_one2one_conflict_delete(self):
+        SSN.objects.create(person=self.a, number='1')
+        SSN.objects.create(person=self.b, number='2')
+
+        merge(self.a, self.b, DELETE)
+
+        assert Person.objects.get(pk=self.b.pk).ssn.number == '1'
+        assert SSN.objects.count() == 1
+
     def test_many2many_simple(self):
         self.g.people.add(self.a)
         merge(self.a, self.b)