diff --git a/stack.yaml b/stack.yaml
index 9f00e8a31..8841429aa 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1,6 +1,6 @@
 # For more information, see: https://github.com/commercialhaskell/stack/blob/release/doc/yaml_configuration.md
 
-resolver: lts-9.11
+resolver: lts-9.20
 packages:
 - '.'
 extra-deps: