diff --git a/statsig/statsig_user.py b/statsig/statsig_user.py
index eee46f3..175b415 100644
--- a/statsig/statsig_user.py
+++ b/statsig/statsig_user.py
@@ -2,9 +2,11 @@
 
 from statsig import statsig_environment_tier
 
+
 def _str_or_none(field):
     return str(field) if field is not None else None
 
+
 @dataclass
 class StatsigUser:
     """An object of properties relating to the current user
@@ -26,9 +28,10 @@ class StatsigUser:
     _statsig_environment: dict = None
 
     def __post_init__(self):
-        if self.user_id is None or self.user_id == "":
+        # ensure there is a user id or at least a custom ID, empty dict evaluates to false in python so we can use "not" operator to check
+        if (self.user_id is None or self.user_id == "") and (self.custom_ids is None or not self.custom_ids):
             raise ValueError(
-                'user_id is required: learn more https://docs.statsig.com/messages/serverRequiredUserID')
+                'user_id or at least a custom ID is required: learn more https://docs.statsig.com/messages/serverRequiredUserID')
 
     def to_dict(self, forEvaluation=False):
         user_nullable = {
@@ -61,5 +64,3 @@ def _get_environment(self):
             return {'tier': tier.value}
 
         return None
-
-    
\ No newline at end of file
diff --git a/tests/test_bad_input.py b/tests/test_bad_input.py
index cf1308e..e7ab1fc 100644
--- a/tests/test_bad_input.py
+++ b/tests/test_bad_input.py
@@ -20,14 +20,20 @@ def test_bad_key(self):
     def test_no_user_id(self):
         with self.assertRaises(ValueError) as context:
             StatsigUser("")
-
         self.assertTrue('user_id' in str(context.exception))
 
         with self.assertRaises(ValueError) as context:
             StatsigUser(None)
+        self.assertTrue('user_id' in str(context.exception))
 
+        with self.assertRaises(ValueError) as context:
+            StatsigUser(None, custom_ids=dict())
         self.assertTrue('user_id' in str(context.exception))
 
+        user = StatsigUser(None, custom_ids=dict(stableID='123'))
+        self.assertFalse(user.user_id)
+        self.assertTrue(user.custom_ids)
+
     def test_invalid_tier(self):
         with self.assertRaises(ValueError) as context:
             StatsigOptions(tier=123)