diff --git a/build-constraints.yaml b/build-constraints.yaml
index fdebbe0f..45ca8cb8 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -897,6 +897,9 @@ packages:
         - repa-algorithms < 3.4
         - repa-io < 3.4
 
+        # https://github.com/Happstack/happstack-server/issues/6
+        - happstack-server < 7.4.3
+
 # Package flags are applied to individual packages, and override the values of
 # global-flags
 package-flags: