diff --git a/build-constraints.yaml b/build-constraints.yaml
index f0ecea98..70906053 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -477,6 +477,7 @@ packages:
         - matrix-market-attoparsec
         - mwc-probability-transition < 0 # via logging-effect
         - xeno
+        - bytestring-mmap # required by xeno
         - datasets < 0 # via req
         - lucid-extras
         - rigel-viz