diff --git a/.mypy.ini b/.mypy.ini
index c13cdf5b4..325b624d0 100644
--- a/.mypy.ini
+++ b/.mypy.ini
@@ -44,6 +44,8 @@ strict_optional = True
 strict_optional = True
 [mypy-aqt.preferences]
 strict_optional = True
+[mypy-aqt.overview]
+strict_optional = True
 [mypy-aqt.customstudy]
 strict_optional = True
 [mypy-anki.scheduler.base]
diff --git a/qt/aqt/overview.py b/qt/aqt/overview.py
index 20d276dbb..da017714f 100644
--- a/qt/aqt/overview.py
+++ b/qt/aqt/overview.py
@@ -224,13 +224,14 @@ class Overview:
             dyn = ""
         return f'<div class="descfont descmid description {dyn}">{desc}</div>'
 
-    def _table(self) -> str | None:
+    def _table(self) -> str:
         counts = list(self.mw.col.sched.counts())
         current_did = self.mw.col.decks.get_current_id()
         deck_node = self.mw.col.sched.deck_due_tree(current_did)
 
         but = self.mw.button
         if self.mw.col.v3_scheduler():
+            assert deck_node is not None
             buried_new = deck_node.new_count - counts[0]
             buried_learning = deck_node.learn_count - counts[1]
             buried_review = deck_node.review_count - counts[2]