diff --git a/build-constraints.yaml b/build-constraints.yaml
index f40302da..2053b8a0 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -8273,6 +8273,7 @@ expected-test-failures:
     - megaparsec-tests # 9.2.0
     - mighty-metropolis # https://github.com/jtobin/mighty-metropolis/issues/6
     - mixpanel-client # https://github.com/domenkozar/mixpanel-client/issues/7
+    - mmark-ext # https://github.com/mmark-md/mmark-ext/issues/28
     - morpheus-graphql-app
     - mwc-random
     - nettle # https://github.com/stbuehler/haskell-nettle/issues/10