diff --git a/build-constraints.yaml b/build-constraints.yaml
index 13b55a4c..fbafff3e 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -669,6 +669,9 @@ packages:
         # https://github.com/fpco/stackage/issues/398
         - monoid-subclasses < 0.4
 
+        # https://github.com/fpco/stackage/issues/401
+        - happstack-server < 7.4
+
 # Package flags are applied to individual packages, and override the values of
 # global-flags
 package-flags: