diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 68bbb03a..abe21139 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -7,8 +7,8 @@ on:
     - master
   workflow_dispatch:
 
-# As of 27 August 2023, ubuntu-latest and windows-latest come with Stack 2.11.1
-# and macos-latest comes with Stack 2.9.3.
+# As of 27 September 2023, ubuntu-latest and windows-latest come with
+# Stack 2.11.1 and macos-latest comes with Stack 2.9.3.
 
 jobs:
   build:
@@ -22,12 +22,12 @@ jobs:
         resolver:
         - stack-ghc-9.2.8.yaml
         - stack-ghc-9.4.7.yaml
-        - stack-ghc-9.6.2.yaml
+        - stack-ghc-9.6.3.yaml
         include:
         - os: macos-latest
-          resolver: stack-ghc-9.6.2.yaml
+          resolver: stack-ghc-9.6.3.yaml
         - os: windows-latest
-          resolver: stack-ghc-9.6.2.yaml
+          resolver: stack-ghc-9.6.3.yaml
     steps:
     - name: Clone project
       uses: actions/checkout@v3
diff --git a/stack-ghc-9.4.7.yaml b/stack-ghc-9.4.7.yaml
index 57d191fc..244ddc7f 100644
--- a/stack-ghc-9.4.7.yaml
+++ b/stack-ghc-9.4.7.yaml
@@ -1,5 +1,5 @@
 # Snapshot specification for GHC 9.4.7.
-resolver: lts-21.12 # GHC 9.4.7
+resolver: lts-21.13 # GHC 9.4.7
 
 packages:
 - aeson-warning-parser-0.1.0@sha256:f2c1c42b73aa35d352060abcbb867c410cbbf57d0cb0fed607bcd1e2a74954ad,1308
@@ -9,16 +9,16 @@ packages:
 - crypton-x509-store-1.6.9@sha256:422b9b9f87a7382c66385d047615b16fc86a68c08ea22b1e0117c143a2d44050,1750
 - crypton-x509-system-1.6.7@sha256:023ed573d82983bc473a37a89e0434a085b413be9f68d07e085361056afd4637,1532
 - crypton-x509-validation-1.6.12@sha256:85989721b64be4b90de9f66ef641c26f57575cffed1a50d707065fb60176f386,2227
-# lts-21.12 provides hpack-0.35.2
-- hpack-0.35.5@sha256:22b46f28b53ec6fb2d05517b569a74b8b3e5e8c2e89c6b7ca25b345af62f22fa,5119
-# lts-21.12 provides http-client-tls-0.3.6.1
+# lts-21.13 provides hpack-0.35.2
+- hpack-0.36.0@sha256:c2daa6556afc57367a5d1dbd878bf515d442d201e24b27473051359abd47ed08,5187
+# lts-21.13 provides http-client-tls-0.3.6.1
 - http-client-tls-0.3.6.3@sha256:a5909ce412ee65c141b8547f8fe22236f175186c95c708e86a46b5547394f910,2046
-# lts-21.12 provides http-download-0.2.0.0
+# lts-21.13 provides http-download-0.2.0.0
 - http-download-0.2.1.0@sha256:a97863e96f7d44efc3d0e3061db7fe2540b8374ca44ae90d0b56040140cb7506,1716
 - static-bytes-0.1.0@sha256:35dbf30f617baa0151682c97687042516be07872a39984f9fe31f78125b962bf,1627
-# lts-21.12 provides tar-conduit-0.3.2.1
+# lts-21.13 provides tar-conduit-0.3.2.1
 - tar-conduit-0.4.0@sha256:f333649770f5ec42a83a93b0d424cf6bb895d80dfbee05a54340395f81d036ae,3126
-# crypton-connection-0.3.1 requires tls >= 1.7. lts-21.12 provides tls-1.6.0
+# crypton-connection-0.3.1 requires tls >= 1.7. lts-21.13 provides tls-1.6.0
 - tls-1.8.0@sha256:0ea435fb1969384c76e6b6ba49c509cec55eec29f60dd2c335151d9c8a4e8b4f,5571
 
 flags:
diff --git a/stack-ghc-9.6.2.yaml b/stack-ghc-9.6.2.yaml
deleted file mode 100644
index 8e664d21..00000000
--- a/stack-ghc-9.6.2.yaml
+++ /dev/null
@@ -1,6 +0,0 @@
-# Snapshot specification for GHC 9.6.2.
-resolver: nightly-2023-09-17 # GHC 9.6.2
-
-flags:
-  hackage-security:
-    cabal-syntax: true
diff --git a/stack-ghc-9.6.3.yaml b/stack-ghc-9.6.3.yaml
new file mode 100644
index 00000000..f553706a
--- /dev/null
+++ b/stack-ghc-9.6.3.yaml
@@ -0,0 +1,7 @@
+# Snapshot specification for GHC 9.6.3.
+resolver: nightly-2023-09-27 # GHC 9.6.2
+compiler: ghc-9.6.3
+
+flags:
+  hackage-security:
+    cabal-syntax: true
diff --git a/stack.yaml.lock b/stack.yaml.lock
index 288cf94b..ec0bce39 100644
--- a/stack.yaml.lock
+++ b/stack.yaml.lock
@@ -54,12 +54,12 @@ packages:
   original:
     hackage: crypton-x509-validation-1.6.12@sha256:85989721b64be4b90de9f66ef641c26f57575cffed1a50d707065fb60176f386,2227
 - completed:
-    hackage: hpack-0.35.5@sha256:22b46f28b53ec6fb2d05517b569a74b8b3e5e8c2e89c6b7ca25b345af62f22fa,5119
+    hackage: hpack-0.36.0@sha256:c2daa6556afc57367a5d1dbd878bf515d442d201e24b27473051359abd47ed08,5187
     pantry-tree:
-      sha256: d129102d5c4a66111877f48f6f4ba93615df574eb85195faf185c53a3cb215bd
+      sha256: 981e8f8ab3dc8305c5131f4686c835f55d4a841abcc867bfdcbf9e6757e9a638
       size: 3742
   original:
-    hackage: hpack-0.35.5@sha256:22b46f28b53ec6fb2d05517b569a74b8b3e5e8c2e89c6b7ca25b345af62f22fa,5119
+    hackage: hpack-0.36.0@sha256:c2daa6556afc57367a5d1dbd878bf515d442d201e24b27473051359abd47ed08,5187
 - completed:
     hackage: http-client-tls-0.3.6.3@sha256:a5909ce412ee65c141b8547f8fe22236f175186c95c708e86a46b5547394f910,2046
     pantry-tree:
@@ -97,7 +97,7 @@ packages:
     hackage: tls-1.8.0@sha256:0ea435fb1969384c76e6b6ba49c509cec55eec29f60dd2c335151d9c8a4e8b4f,5571
 snapshots:
 - completed:
-    sha256: 9313df78f49519315342f4c51ffc5da12659d3735f8ac3c54a1fb98ff874474e
-    size: 640036
-    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/21/12.yaml
-  original: lts-21.12
+    sha256: 8017c7970c2a8a9510c60cc70ac245d59e0c34eb932b91d37af09fe59855d854
+    size: 640038
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/21/13.yaml
+  original: lts-21.13