diff --git a/stack.yaml b/stack.yaml
index 1d9e84d..042d516 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -2,4 +2,4 @@ flags: {}
 packages:
 - '.'
 extra-deps: [cond-0.4.1.1,murmur3-1.0.3]
-resolver: lts-9.14
+resolver: lts-9.21