diff --git a/build-constraints.yaml b/build-constraints.yaml
index fd184f0f..3fc39b50 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -6820,6 +6820,9 @@ packages:
       - stripe-scotty < 1.1.0.1
       - stripe-wreq < 1.0.1.12
 
+      # https://github.com/commercialhaskell/stackage/issues/6312
+      - sydtest < 0.6
+
 # end of packages
 
 # Package flags are applied to individual packages, and override the values of