diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index c328b031..239c9732 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -15,24 +15,16 @@ jobs:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
         args:
-        - "--resolver nightly"
+        #- "--resolver nightly"
+        - "--resolver lts-18"
         - "--resolver lts-16"
         - "--resolver lts-14"
         - "--resolver lts-12"
         - "--resolver lts-11"
-        - "--stack-yaml stack-persistent-211.yaml"
-        - "--stack-yaml stack-persistent-212.yaml"
-        - "--stack-yaml stack-persistent-213.yaml"
         # Bugs in GHC make it crash too often to be worth running
         exclude:
           - os: windows-latest
             args: "--resolver nightly"
-          - os: windows-latest
-            args: "--resolver lts-16"
-          - os: windows-latest
-            args: "--stack-yaml stack-persistent-211.yaml"
-          - os: windows-latest
-            args: "--stack-yaml stack-persistent-212.yaml"
 
     steps:
       - name: Clone project
@@ -51,6 +43,8 @@ jobs:
         shell: bash
         run: |
             set -ex
-            stack upgrade
-            stack --version
-            stack test --fast --no-terminal ${{ matrix.args }}
+            mkdir -p ../_newstack
+            stack upgrade --force-download --local-bin-path ../_newstack
+            ../_newstack/stack --version
+            ../_newstack/stack
+            ../_newstack/stack test --fast --no-terminal ${{ matrix.args }}
diff --git a/stack-persistent-211.yaml b/stack-persistent-211.yaml
deleted file mode 100644
index 883223ba..00000000
--- a/stack-persistent-211.yaml
+++ /dev/null
@@ -1,20 +0,0 @@
-resolver: lts-16.20
-packages:
-- ./yesod-core
-- ./yesod-static
-- ./yesod-persistent
-- ./yesod-newsfeed
-- ./yesod-form
-- ./yesod-form-multi
-- ./yesod-auth
-- ./yesod-auth-oauth
-- ./yesod-sitemap
-- ./yesod-test
-- ./yesod-bin
-- ./yesod
-- ./yesod-eventsource
-- ./yesod-websockets
-extra-deps:
-- persistent-2.11.0.1@rev:0
-- persistent-template-2.9.1.0@rev:0
-- persistent-sqlite-2.11.0.0@rev:0
diff --git a/stack-persistent-212.yaml b/stack-persistent-212.yaml
deleted file mode 100644
index b4087765..00000000
--- a/stack-persistent-212.yaml
+++ /dev/null
@@ -1,20 +0,0 @@
-resolver: nightly-2021-03-31
-packages:
-- ./yesod-core
-- ./yesod-static
-- ./yesod-persistent
-- ./yesod-newsfeed
-- ./yesod-form
-- ./yesod-form-multi
-- ./yesod-auth
-- ./yesod-auth-oauth
-- ./yesod-sitemap
-- ./yesod-test
-- ./yesod-bin
-- ./yesod
-- ./yesod-eventsource
-- ./yesod-websockets
-extra-deps:
-- persistent-2.12.0.1
-- persistent-template-2.12.0.0
-- persistent-sqlite-2.12.0.0
diff --git a/stack-persistent-213.yaml b/stack-persistent-213.yaml
deleted file mode 100644
index c90d12e7..00000000
--- a/stack-persistent-213.yaml
+++ /dev/null
@@ -1,23 +0,0 @@
-resolver: nightly-2021-03-31
-packages:
-- ./yesod-core
-- ./yesod-static
-- ./yesod-persistent
-- ./yesod-newsfeed
-- ./yesod-form
-- ./yesod-form-multi
-- ./yesod-auth
-- ./yesod-auth-oauth
-- ./yesod-sitemap
-- ./yesod-test
-- ./yesod-bin
-- ./yesod
-- ./yesod-eventsource
-- ./yesod-websockets
-extra-deps:
-- lift-type-0.1.0.1
-- persistent-2.13.0.0
-- persistent-mysql-2.13.0.0
-- persistent-sqlite-2.13.0.0
-- persistent-postgresql-2.13.0.0
-- persistent-template-2.12.0.0
diff --git a/stack.yaml b/stack.yaml
index 3aed69da..8078abab 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1,4 +1,4 @@
-resolver: lts-15.5
+resolver: lts-18.3
 packages:
 - ./yesod-core
 - ./yesod-static
diff --git a/stack.yaml.lock b/stack.yaml.lock
index b90ed2d5..7940767f 100644
--- a/stack.yaml.lock
+++ b/stack.yaml.lock
@@ -6,7 +6,7 @@
 packages: []
 snapshots:
 - completed:
-    size: 491372
-    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/15/5.yaml
-    sha256: 1b549cfff328040c382a70a84a2087aac8dab6d778bf92f32a93a771a1980dfc
-  original: lts-15.5
+    size: 585603
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/18/3.yaml
+    sha256: 694573e96dca34db5636edb1fe6c96bb233ca0f9fb96c1ead1671cdfa9bd73e9
+  original: lts-18.3