diff --git a/tap_hubspot/__init__.py b/tap_hubspot/__init__.py
index 2dfef5bb..ea9f3326 100644
--- a/tap_hubspot/__init__.py
+++ b/tap_hubspot/__init__.py
@@ -500,8 +500,10 @@ def sync_contacts(STATE, ctx):
 
             if not modified_time or modified_time >= start:
                 vids.append(row['vid'])
-                # Adding replication key value in `bookmark_values` dict
-                # Here, key is vid(primary key) and value is replication key value.
+
+            # Adding replication key value in `bookmark_values` dict
+            # Here, key is vid(primary key) and value is replication key value.
+            if modified_time:
                 bookmark_values[row['vid']] = utils.strftime(modified_time)
 
             if modified_time and modified_time >= max_bk_value:
diff --git a/tests/unittests/test_contacts.py b/tests/unittests/test_contacts.py
new file mode 100644
index 00000000..e53fa4ba
--- /dev/null
+++ b/tests/unittests/test_contacts.py
@@ -0,0 +1,72 @@
+import os
+import unittest
+from tap_hubspot import acquire_access_token_from_refresh_token
+from tap_hubspot import CONFIG
+from tap_hubspot import Context
+from tap_hubspot import gen_request
+from tap_hubspot import get_url
+from tap_hubspot import load_schema
+from tap_hubspot import merge_responses
+from tap_hubspot import process_v3_deals_records
+from tap_hubspot import sync_contacts
+from unittest import mock
+
+import logging
+logging.getLogger().level = logging.INFO
+
+
+class TestContacts(unittest.TestCase):
+
+    def setUp(self):
+        self.maxDiff = None
+
+    @mock.patch("singer.write_record")
+    @mock.patch("tap_hubspot.request")
+    @mock.patch("tap_hubspot.gen_request")
+    @mock.patch("tap_hubspot.load_schema")
+    def test_bookmarking(self, fake_load_schema, fake_gen_request, fake_request, fake_write_record):
+        self.maxDiff = None
+        state = {
+            "bookmarks": {
+                "contacts": {
+                    "updated_at": "2022-09-26T00:00:00Z"
+                }
+            }
+        }
+        state = {
+            "bookmarks": {
+                "contacts": {
+                    "versionTimestamp": "2022-09-26T00:00:00Z"}
+                },
+
+        }
+        catalog = {"streams": [
+            {"tap_stream_id": "contacts",
+             "metadata": [],
+             "schema": {}}
+        ]}
+        ctx = Context(catalog)
+
+        fake_load_schema.return_value = {}
+        fake_gen_request.return_value = [
+            {"vid": 1},
+            {"vid": 2},
+            {"vid": 3, "versionTimestamp": "2022-09-26T12:00:00Z"},
+        ]
+
+        fake_request.return_value.json.return_value.values.return_value = [
+            {"vid": 1},
+            {"vid": 2},
+            {"vid": 3},
+        ]
+
+        sync_contacts(state, ctx)
+        actual = [x[0][1] for x in fake_write_record.call_args_list]
+
+        expected = [
+            {'vid': 1, 'versionTimestamp': None},
+            {'vid': 2, 'versionTimestamp': None},
+            {'vid': 3, 'versionTimestamp': '2022-09-26T12:00:00.000000Z'}
+        ]
+
+        self.assertEqual(expected, actual)