diff --git a/stack.yaml b/stack.yaml
index 9c8a04c8a..7458bf26f 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -23,7 +23,8 @@ extra-deps:
 - ghc-boot-9.10.1@rev:1
 - process-1.6.25.0
 - time-1.12.2
-- unix-2.8.6.0
+- unix-2.8.5.1
+#- unix-2.8.6.0
 # for windows
 - Win32-2.14.0.0
 # for hledger