diff --git a/axes/attempts.py b/axes/attempts.py
index e3e1904..0e73e16 100644
--- a/axes/attempts.py
+++ b/axes/attempts.py
@@ -21,10 +21,13 @@ def get_cool_off_threshold(attempt_time: datetime = None) -> datetime:
     Get threshold for fetching access attempts from the database.
     """
 
-    if attempt_time is None:
-        return now() - get_cool_off()
+    cool_off = get_cool_off()
+    if cool_off is None:
+        raise TypeError('Cool off threshold can not be calculated with settings.AXES_COOLOFF_TIME set to None')
 
-    return attempt_time - get_cool_off()
+    if attempt_time is None:
+        return now() - cool_off
+    return attempt_time - cool_off
 
 
 def filter_user_attempts(request: AxesHttpRequest, credentials: dict = None) -> QuerySet:
diff --git a/axes/tests/test_attempts.py b/axes/tests/test_attempts.py
index 7560b30..6cc1a76 100644
--- a/axes/tests/test_attempts.py
+++ b/axes/tests/test_attempts.py
@@ -2,13 +2,35 @@ from unittest.mock import patch
 
 from django.contrib.auth import get_user_model
 from django.http import HttpRequest
+from django.test import override_settings
+from django.utils.timezone import now
 
-from axes.attempts import is_user_attempt_whitelisted
+from axes.attempts import is_user_attempt_whitelisted, get_cool_off_threshold
 from axes.models import AccessAttempt
 from axes.tests.base import AxesTestCase
 from axes.utils import reset
 
 
+class GetCoolOffThresholdTestCase(AxesTestCase):
+    @override_settings(AXES_COOLOFF_TIME=42)
+    def test_get_cool_off_threshold(self):
+        timestamp = now()
+
+        with patch('axes.attempts.now', return_value=timestamp):
+            attempt_time = timestamp
+            threshold_now = get_cool_off_threshold(attempt_time)
+
+            attempt_time = None
+            threshold_none = get_cool_off_threshold(attempt_time)
+
+        self.assertEqual(threshold_now, threshold_none)
+
+    @override_settings(AXES_COOLOFF_TIME=None)
+    def test_get_cool_off_threshold_error(self):
+        with self.assertRaises(TypeError):
+            get_cool_off_threshold()
+
+
 class ResetTestCase(AxesTestCase):
     def test_reset(self):
         self.create_attempt()