diff --git a/anki/cards.py b/anki/cards.py
index ee9f7b8c1..5d8e2fb18 100644
--- a/anki/cards.py
+++ b/anki/cards.py
@@ -4,19 +4,10 @@
 import pprint
 
 import time
+from anki.hooks import runHook
 from anki.utils import intTime, timestampID, joinFields
 from anki.consts import *
 
-# temporary
-_warned = False
-def warn():
-    global _warned
-    if _warned:
-        return
-    import sys
-    sys.stderr.write("Ignore the above, please download the fix assertion addon.")
-    _warned = True
-
 # Cards
 ##########################################################################
 
@@ -83,7 +74,7 @@ class Card(object):
         self.usn = self.col.usn()
         # bug check
         if self.queue == 2 and self.odue and not self.col.decks.isDyn(self.did):
-            warn()
+            runHook("odueInvalid")
         assert self.due < 4294967296
         self.col.db.execute(
             """
@@ -114,7 +105,7 @@ insert or replace into cards values
         self.usn = self.col.usn()
         # bug checks
         if self.queue == 2 and self.odue and not self.col.decks.isDyn(self.did):
-            warn()
+            runHook("odueInvalid")
         assert self.due < 4294967296
         self.col.db.execute(
             """update cards set
diff --git a/anki/collection.py b/anki/collection.py
index 706c0ff78..fba9d5899 100644
--- a/anki/collection.py
+++ b/anki/collection.py
@@ -741,6 +741,16 @@ select id from cards where nid not in (select id from notes)""")
                 ngettext("Deleted %d card with missing note.",
                          "Deleted %d cards with missing note.", cnt) % cnt)
             self.remCards(ids)
+        # cards with odue set when it shouldn't be
+        ids = self.db.list("""
+select id from cards where odue > 0 and (type=1 or queue=2) and not odid""")
+        if ids:
+            cnt = len(ids)
+            problems.append(
+                ngettext("Fixed %d card with invalid properties.",
+                         "Fixed %d cards with invalid properties.", cnt) % cnt)
+            self.db.execute("update cards set odue=0 where id in "+
+                ids2str(ids))
         # tags
         self.tags.registerNotes()
         # field cache
diff --git a/anki/sched.py b/anki/sched.py
index 2f52e557e..189dd1582 100644
--- a/anki/sched.py
+++ b/anki/sched.py
@@ -1334,7 +1334,7 @@ and (queue=0 or (queue=2 and due<=?))""",
     def forgetCards(self, ids):
         "Put cards at the end of the new queue."
         self.col.db.execute(
-            "update cards set type=0,queue=0,ivl=0,due=0,factor=? where odid=0 "
+            "update cards set type=0,queue=0,ivl=0,due=0,odue=0,factor=? where odid=0 "
             "and queue >= 0 and id in "+ids2str(ids), 2500)
         pmax = self.col.db.scalar(
             "select max(due) from cards where type=0") or 0
diff --git a/aqt/main.py b/aqt/main.py
index 395346e72..63fee896f 100644
--- a/aqt/main.py
+++ b/aqt/main.py
@@ -863,6 +863,12 @@ Difference to correct time: %s.""") % diffText
     def setupHooks(self):
         addHook("modSchema", self.onSchemaMod)
         addHook("remNotes", self.onRemNotes)
+        addHook("odueInvalid", self.onOdueInvalid)
+
+    def onOdueInvalid(self):
+        showWarning(_("""\
+Invalid property found on card. Please use Tools>Check Database, \
+and if the problem comes up again, please ask on the support site."""))
 
     # Log note deletion
     ##########################################################################