diff --git a/build-constraints.yaml b/build-constraints.yaml
index bd4bd03d..5479e9c4 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -3998,7 +3998,7 @@ packages:
         - genvalidity-hspec-hashable
         - genvalidity-hspec-optics
         - genvalidity-hspec-persistent
-        - genvalidity-mergeful
+        - genvalidity-mergeful < 0 # via mergeful
         - genvalidity-mergeless
         - genvalidity-path
         - genvalidity-persistent
@@ -4015,8 +4015,8 @@ packages:
         - genvalidity-unordered-containers
         - genvalidity-uuid
         - genvalidity-vector
-        - mergeful
-        - mergeful-persistent
+        - mergeful < 0 # https://github.com/commercialhaskell/stackage/issues/6565
+        - mergeful-persistent < 0 # via mergeful
         - mergeless
         - mergeless-persistent
         - pretty-relative-time