diff --git a/.github/workflows/haskell_stack.yaml b/.github/workflows/haskell_stack.yaml
index 957f57a..736b6ff 100644
--- a/.github/workflows/haskell_stack.yaml
+++ b/.github/workflows/haskell_stack.yaml
@@ -22,6 +22,7 @@ jobs:
           - lts-18
           - lts-19
           - lts-20
+          - lts-21
         experimental:
           - false
         include:
diff --git a/stack-lts-21.yaml b/stack-lts-21.yaml
new file mode 100644
index 0000000..e1c250b
--- /dev/null
+++ b/stack-lts-21.yaml
@@ -0,0 +1,5 @@
+resolver: lts-21.14
+packages:
+- .
+extra-deps:
+- attoparsec-aeson-2.1.0.0@sha256:fa83aba43bfa58490de8f274d19b9d58b6403a207b12cac5f93922102b084c52,1154
diff --git a/stack-lts-21.yaml.lock b/stack-lts-21.yaml.lock
new file mode 100644
index 0000000..162b6fb
--- /dev/null
+++ b/stack-lts-21.yaml.lock
@@ -0,0 +1,19 @@
+# This file was autogenerated by Stack.
+# You should not edit this file by hand.
+# For more information, please see the documentation at:
+#   https://docs.haskellstack.org/en/stable/lock_files
+
+packages:
+- completed:
+    hackage: attoparsec-aeson-2.1.0.0@sha256:fa83aba43bfa58490de8f274d19b9d58b6403a207b12cac5f93922102b084c52,1154
+    pantry-tree:
+      sha256: 294c3a8a19a7ddad58097e18c624c6b34894b3c4a4cc490759cb31d842db242a
+      size: 114
+  original:
+    hackage: attoparsec-aeson-2.1.0.0@sha256:fa83aba43bfa58490de8f274d19b9d58b6403a207b12cac5f93922102b084c52,1154
+snapshots:
+- completed:
+    sha256: 60e54c1ba3c1e7163acf6dafa9d56b2d3b23f88a31ad53a1c9d888f32561f8da
+    size: 639819
+    url: https://github.com/raw/commercialhaskell/stackage-snapshots/master/lts/21/14.yaml
+  original: lts-21.14