diff --git a/.github/workflows/latest_deps.yml b/.github/workflows/latest_deps.yml
index ec6391cf8..7b839f59c 100644
--- a/.github/workflows/latest_deps.yml
+++ b/.github/workflows/latest_deps.yml
@@ -57,8 +57,8 @@ jobs:
       # `pip install matrix-synapse[all]` as closely as possible.
       - run: poetry update --no-dev
       - run: poetry run pip list > after.txt && (diff -u before.txt after.txt || true)
-      - name: Remove warn_unused_ignores from mypy config
-        run: sed '/warn_unused_ignores = True/d' -i mypy.ini
+      - name: Remove unhelpful options from mypy config
+        run: sed -e '/warn_unused_ignores = True/d' -e '/warn_redundant_casts = True/d' -i mypy.ini
       - run: poetry run mypy
   trial:
     needs: check_repo
diff --git a/changelog.d/16213.misc b/changelog.d/16213.misc
new file mode 100644
index 000000000..8c14f5fd5
--- /dev/null
+++ b/changelog.d/16213.misc
@@ -0,0 +1 @@
+Fix the latest-deps CI job.