diff --git a/mockfirestore/document.py b/mockfirestore/document.py
index 24aa433..808959f 100644
--- a/mockfirestore/document.py
+++ b/mockfirestore/document.py
@@ -23,6 +23,8 @@ def exists(self) -> bool:
         return self._doc != {}
 
     def to_dict(self) -> Document:
+        if not self.exists:
+            return None
         return self._doc
 
     @property
diff --git a/tests/test_document_reference.py b/tests/test_document_reference.py
index c582b36..d3ff43c 100644
--- a/tests/test_document_reference.py
+++ b/tests/test_document_reference.py
@@ -52,7 +52,7 @@ def test_document_get_documentDoesNotExist(self):
         fs = MockFirestore()
         fs._data = {'foo': {}}
         doc = fs.collection('foo').document('bar').get().to_dict()
-        self.assertEqual({}, doc)
+        self.assertIsNone(doc)
 
     def test_get_nestedDocument(self):
         fs = MockFirestore()