diff --git a/build-constraints.yaml b/build-constraints.yaml
index 3ca7b22d..29658eaf 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -1645,7 +1645,7 @@ packages:
         - ptr-poker
         - rebase
         - rerebase
-        - slave-thread
+        - slave-thread < 0 # https://github.com/nikita-volkov/slave-thread/issues/21
         - stm-containers
         - stm-hamt
         - template-haskell-compat-v0208