diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 7626b83d..9ab46d89 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -7,8 +7,8 @@ on:
     - master
   workflow_dispatch:
 
-# As of 23 March 2024, ubuntu-latest, windows-latest and macos-latest come
-# with Stack 2.13.3. However, macos-14 does not come with Haskell tools.
+# As of 6 May 2024, ubuntu-latest and windows-latest come with Stack 2.15.5.
+# However, macos-13 and macos-latest do not come with Haskell tools.
 
 jobs:
   build:
@@ -21,13 +21,13 @@ jobs:
         - ubuntu-latest
         snapshot:
         - stack-ghc-9.4.8.yaml
-        - stack-ghc-9.6.4.yaml
+        - stack-ghc-9.6.5.yaml
         - stack-ghc-9.8.2.yaml
         include:
-        - os: macos-latest
+        - os: macos-13
           snapshot: stack-ghc-9.8.2.yaml
-        # macos-14 provides macOS/AArch64 (M1)
-        - os: macos-14
+        # macos-latest provides macOS/AArch64 (M1)
+        - os: macos-latest
           snapshot: stack-ghc-9.8.2.yaml
         - os: windows-latest
           snapshot: stack-ghc-9.8.2.yaml
@@ -53,9 +53,9 @@ jobs:
       run: |
         set -ex
 
-        if [[ "${{ matrix.os }}" == "macos-14" ]]
+        if [[ "${{ matrix.os }}" == "macos-13" || "${{ matrix.os }}" == "macos-latest" ]]
         then
-          # macos-14 does not include Haskell tools as at 2024-03-23.
+          # macos-13 and macos-latest do not include Haskell tools as at 2024-05-06.
           curl -sSL https://get.haskellstack.org/ | sh
         fi
 
diff --git a/stack-ghc-9.2.8.yaml b/stack-ghc-9.2.8.yaml
index 55962672..069f5b38 100644
--- a/stack-ghc-9.2.8.yaml
+++ b/stack-ghc-9.2.8.yaml
@@ -30,5 +30,3 @@ packages:
 flags:
   ansi-terminal:
     win32-2-13-1: false
-  mintty:
-    win32-2-13-1: false
diff --git a/stack-ghc-9.4.8.yaml b/stack-ghc-9.4.8.yaml
index de12e2e0..d9decb08 100644
--- a/stack-ghc-9.4.8.yaml
+++ b/stack-ghc-9.4.8.yaml
@@ -20,11 +20,3 @@ packages:
 - tar-conduit-0.4.1@sha256:112d28118eb71901ea9e224e1b174c648b378256729669c2739b8b803d25b43a,3126
 # crypton-connection-0.3.1 requires tls >= 1.7. lts-21.25 provides tls-1.6.0
 - tls-1.8.0@sha256:0ea435fb1969384c76e6b6ba49c509cec55eec29f60dd2c335151d9c8a4e8b4f,5571
-
-flags:
-  ansi-terminal:
-    win32-2-13-1: false
-  hackage-security:
-    cabal-syntax: true
-  mintty:
-    win32-2-13-1: false
diff --git a/stack-ghc-9.6.4.yaml b/stack-ghc-9.6.4.yaml
deleted file mode 100644
index 5b3b8c8c..00000000
--- a/stack-ghc-9.6.4.yaml
+++ /dev/null
@@ -1,6 +0,0 @@
-# Snapshot specification for GHC 9.6.4.
-snapshot: lts-22.13 # GHC 9.6.4
-
-flags:
-  hackage-security:
-    cabal-syntax: true
diff --git a/stack-ghc-9.6.5.yaml b/stack-ghc-9.6.5.yaml
new file mode 100644
index 00000000..00e8e5fb
--- /dev/null
+++ b/stack-ghc-9.6.5.yaml
@@ -0,0 +1,2 @@
+# Snapshot specification for GHC 9.6.5.
+snapshot: lts-22.21 # GHC 9.6.5
diff --git a/stack-ghc-9.8.2.yaml b/stack-ghc-9.8.2.yaml
index 8d956f4f..54416d57 100644
--- a/stack-ghc-9.8.2.yaml
+++ b/stack-ghc-9.8.2.yaml
@@ -1,6 +1,2 @@
 # Snapshot specification for GHC 9.8.2.
-snapshot: nightly-2024-03-20 # GHC 9.8.2
-
-flags:
-  hackage-security:
-    cabal-syntax: true
+snapshot: nightly-2024-05-06 # GHC 9.8.2
diff --git a/stack.yaml b/stack.yaml
index c0fbaec4..16075296 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1 +1 @@
-snapshot: stack-ghc-9.6.4.yaml
+snapshot: stack-ghc-9.6.5.yaml
diff --git a/stack.yaml.lock b/stack.yaml.lock
index fcf6d2a6..ee7289b7 100644
--- a/stack.yaml.lock
+++ b/stack.yaml.lock
@@ -6,7 +6,7 @@
 packages: []
 snapshots:
 - completed:
-    sha256: 6f0bea3ba5b07360f25bc886e8cff8d847767557a492a6f7f6dcb06e3cc79ee9
-    size: 712905
-    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/22/13.yaml
-  original: lts-22.13
+    sha256: b146f371d1a90abbd2aeae1da10f776951046be50eae55a6fe93548a74fcc0dd
+    size: 713338
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/22/21.yaml
+  original: lts-22.21