diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index d78c83fd..9a7a3453 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -102,11 +102,12 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        resolver: [nightly, lts-22, lts-21, lts-20, lts-19, lts-18, lts-16, lts-14, lts-12, lts-11]
+        resolver: [nightly, lts-22, lts-21, lts-20, lts-19, lts-18, lts-16, lts-14, lts-12, lts-11, lts-9]
         include:
+          - resolver: lts-9
+            stack-yaml: stack-custom.yaml
           - resolver: lts-11
-            ghc: '8.2.2'
-            stack-yaml: stack-old.yaml
+            stack-yaml: stack-custom.yaml
           - resolver: lts-12
             ghc: '8.4.4'
             stack-yaml: stack-old.yaml
@@ -165,7 +166,7 @@ jobs:
             stack-yaml: stack.yaml
     env:
       STACK_YAML: '${{ matrix.stack-yaml }}'
-      STACK_ARGS: '--resolver ${{ matrix.resolver }} --system-ghc'
+      STACK_ARGS: '--resolver ${{ matrix.resolver }}'
       cache-version: v5 # bump up this version to invalidate currently stored cache
     steps:
     - uses: actions/checkout@v4
@@ -176,7 +177,7 @@ jobs:
       with:
         ghc-version: ${{ matrix.ghc }}
         enable-stack: true
-        stack-version: ${{ matrix.resolver == 'lts-11' && '2.15.5' || 'latest' }}
+        stack-version: ${{ (matrix.resolver == 'lts-9' || matrix.resolver == 'lts-11') && '2.15.5' || 'latest' }}
 
     - name: Cache
       id: cache
diff --git a/stack-custom.yaml b/stack-custom.yaml
new file mode 100644
index 00000000..37e69f0d
--- /dev/null
+++ b/stack-custom.yaml
@@ -0,0 +1,19 @@
+resolver: lts-11.22
+packages:
+- .
+extra-deps:
+- splitmix-0.1@sha256:d50c4d0801a35be7875a040470c09863342514930c82a7d25780a6c2efc4fda9,5249
+- rdtsc-1.3.0.1@sha256:0a6e8dc715ba82ad72c7e2b1c2f468999559bec059d50540719a80b00dcc4e66,1557
+- smallcheck-1.2.0@sha256:8b431572e6a0503223e0e52014d41084c1b01f2aeea3bd499f6f529b3f6dfa89,1482
+- tasty-1.3.1@sha256:01e35c97f7ee5ccbc28f21debea02a38cd010d53b4c3087f5677c5d06617a507,2520
+- tasty-hunit-0.10.2@sha256:22bc1122e8256664d7cb1e44c6bcace95676c523179947bf2403db71af43dc6d,1473
+- ansi-wl-pprint-0.6.8.2@sha256:a890b713942c1aa0109fb632e9fee581ceb5b0763fd936ae8cae22e5f91a0877,2178
+- ansi-terminal-0.9.1@sha256:48f53532d0f365ffa568c8cf0adc84c66f800a7d80d3329e4f04fa75392f4af1,3225
+- wcwidth-0.0.2@sha256:77531eb6683c505c22ab3fa11bbc43d3ce1e7dac21401d4d5a19677d348bb5f3,1998
+- tasty-bench-0.2.3@sha256:daa2221a1b1c65990633a51236f1cb4a52cba8ef0f0731f653e712a8bab07616,1319
+- inspection-testing-0.4.5.0@sha256:938e7ce2ef42033071a5e60198c6e19ab61c411f5879b85821247a504f131768,8058
+- tasty-inspection-testing-0.1@sha256:9c5e76345168fd3a59b43d305eebf8df3c792ce324c66bbdee45b54aa7d2c0ad,1214
+- primitive-0.7.4.0@sha256:89b88a3e08493b7727fa4089b0692bfbdf7e1e666ef54635f458644eb8358764,2857
+- vector-0.12.3.1@sha256:fffbd00912d69ed7be9bc7eeb09f4f475e0d243ec43f916a9fd5bbd219ce7f3e,8238
+- data-array-byte-0.1.0.1@sha256:ad89e28b2b046175698fbf542af2ce43e5d2af50aae9f48d12566b1bb3de1d3c,1989
+- optparse-applicative-0.14.2.0@sha256:cfbc2df0d9e144d343ccea6d25ab27543c15ea17d2abcbabcdf76030a2236383,4359
diff --git a/stack-old.yaml b/stack-old.yaml
index 35ca7f5f..f8c19b1c 100644
--- a/stack-old.yaml
+++ b/stack-old.yaml
@@ -1,4 +1,5 @@
 resolver: lts-12.26
+system-ghc: true
 packages:
 - .
 extra-deps:
diff --git a/stack.yaml b/stack.yaml
index 6eda0f02..6036e063 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1,4 +1,5 @@
 resolver: lts-21.25
+system-ghc: true
 packages:
 - .
 extra-deps: []