diff --git a/physics/views.py b/physics/views.py
index 57353e35..e5264164 100644
--- a/physics/views.py
+++ b/physics/views.py
@@ -322,7 +322,7 @@ def exam_take(request, pk, sk, cid, passcode=None):
     if not exam.active:
         raise Http404("Exam not found")
 
-    if exam.valid_users is not None:
+    if exam.valid_users.exists():
         user = exam.valid_users.filter(cid=cid)
 
         if not user or user.passcode != passcode: