diff --git a/storey/sources.py b/storey/sources.py
index 9856a472..787156d5 100644
--- a/storey/sources.py
+++ b/storey/sources.py
@@ -763,7 +763,7 @@ async def _run_loop(self):
                     if isinstance(self._key_field, list):
                         key = []
                         for key_field in self._key_field:
-                            if key_field not in body or body[key_field] is None:
+                            if key_field not in body or pandas.isna(body[key_field]):
                                 create_event = False
                                 break
                             key.append(body[key_field])
diff --git a/tests/test_flow.py b/tests/test_flow.py
index 1352b413..7b0f1f82 100644
--- a/tests/test_flow.py
+++ b/tests/test_flow.py
@@ -2670,6 +2670,39 @@ def test_none_key_is_not_written():
     assert result == expected
 
 
+def test_none_key_num_is_not_written():
+    data = pd.DataFrame({'index': [10, None, 20], 'some_data': [1, 2, 3]})
+    data.set_index(keys=['index'], inplace=True)
+
+    controller = build_flow([
+        DataframeSource(data, key_field=['index']),
+        Reduce([], append_and_return),
+    ]).run()
+    result = controller.await_termination()
+    expected = [{'index': 10, 'some_data': 1}, {'index': 20, 'some_data': 3}]
+
+    assert result == expected
+
+
+def test_none_key_date_is_not_written():
+
+    data = pd.DataFrame({'index': [datetime(2020, 6, 27, 10, 23, 8, 420581),
+                                   None,
+                                   datetime(2020, 6, 28, 10, 23, 8, 420581)],
+                         'some_data': [1, 2, 3]})
+    data.set_index(keys=['index'], inplace=True)
+
+    controller = build_flow([
+        DataframeSource(data, key_field=['index']),
+        Reduce([], append_and_return),
+    ]).run()
+    result = controller.await_termination()
+    expected = [{'index': datetime(2020, 6, 27, 10, 23, 8, 420581), 'some_data': 1},
+                {'index': datetime(2020, 6, 28, 10, 23, 8, 420581), 'some_data': 3}]
+
+    assert result == expected
+
+
 def test_csv_none_value_first_row(tmpdir):
     out_file_par = f'{tmpdir}/test_csv_none_value_first_row_{uuid.uuid4().hex}.parquet'
     out_file_csv = f'{tmpdir}/test_csv_none_value_first_row_{uuid.uuid4().hex}.csv'