diff --git a/compose.yml b/compose.yml
index 018c134..24aa68c 100644
--- a/compose.yml
+++ b/compose.yml
@@ -1,6 +1,6 @@
 services:
   dev:
-    image: ghcr.io/flipstone/haskell-tools:debian-unstable-ghc-9.4.5-2023-07-18-1d8bf61
+    image: ghcr.io/flipstone/haskell-tools:debian-stable-ghc-9.4.6-2023-08-29-52330cd
     volumes:
       - .:${PROJECT_DIR}
       - flipstone_stack_root:/stack-root
diff --git a/stack.yaml b/stack.yaml
index 73375f0..8625b92 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1,4 +1,4 @@
-resolver: lts-21.3
+resolver: lts-21.9
 allow-different-user: true
 system-ghc: true
 install-ghc: false
@@ -17,4 +17,4 @@ flags:
 
 extra-deps:
   - git: https://github.com/flipstone/shrubbery.git
-    commit: 8cd0c45237be047a975d754859fc4b7fb24f49d4 
+    commit: 253a5a954b9117df6b06e32e955f293813db2489
diff --git a/stack.yaml.lock b/stack.yaml.lock
index 5b5da1c..9d564e5 100644
--- a/stack.yaml.lock
+++ b/stack.yaml.lock
@@ -5,19 +5,19 @@
 
 packages:
 - completed:
-    commit: 8cd0c45237be047a975d754859fc4b7fb24f49d4
+    commit: 253a5a954b9117df6b06e32e955f293813db2489
     git: https://github.com/flipstone/shrubbery.git
     name: shrubbery
     pantry-tree:
-      sha256: 48ab4b5d472409264e01166f5e993a98c874393b2caa145921faa7e47248acea
-      size: 1552
+      sha256: dc804a41ddb2243d457b627953134352a45454cd43e4ed892ced0cf0a1ef7502
+      size: 1605
     version: 0.1.2.0
   original:
-    commit: 8cd0c45237be047a975d754859fc4b7fb24f49d4
+    commit: 253a5a954b9117df6b06e32e955f293813db2489
     git: https://github.com/flipstone/shrubbery.git
 snapshots:
 - completed:
-    sha256: 97710f56bf093fca0ee5d8dbe19d96b654c752e405b66795b4baedd84a794c60
-    size: 640010
-    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/21/3.yaml
-  original: lts-21.3
+    sha256: 2fc12a405ab6f7eac73eb11a0ca5ccca0e956bd2848db780c140b7406ff9ebb5
+    size: 640035
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/21/9.yaml
+  original: lts-21.9