diff --git a/pylib/anki/sched.py b/pylib/anki/sched.py
index ff3f0c5d0..c0badf0ac 100644
--- a/pylib/anki/sched.py
+++ b/pylib/anki/sched.py
@@ -74,7 +74,7 @@ class Scheduler(V2):
             self._answerRevCard(card, ease)
             self._updateStats(card, "rev")
         else:
-            raise Exception("Invalid queue")
+            raise Exception("Invalid queue '%s'" % card)
         self._updateStats(card, "time", card.timeTaken())
         card.mod = intTime()
         card.usn = self.col.usn()
diff --git a/pylib/anki/schedv2.py b/pylib/anki/schedv2.py
index cab024770..ab3afdc48 100644
--- a/pylib/anki/schedv2.py
+++ b/pylib/anki/schedv2.py
@@ -104,7 +104,7 @@ class Scheduler:
             # update daily limit
             self._updateStats(card, "rev")
         else:
-            assert 0
+            raise Exception("Invalid queue '%s'" % card)
 
         # once a card has been answered once, the original due date
         # no longer applies