diff --git a/.github/renovate.json5 b/.github/renovate.json5
index 61a6c78..7930d30 100644
--- a/.github/renovate.json5
+++ b/.github/renovate.json5
@@ -100,6 +100,16 @@
         '/docker/docker/',
       ],
     },
+    {
+      // Lock docker to v28.1.1 for Ubuntu 20.04.
+      matchFileNames: [
+        'os/ubuntu-20.04/Earthfile',
+      ],
+      matchPackageNames: [
+        'docker/docker',
+      ],
+      allowedVersions: '28.1.1',
+    },
     {
       // Lock docker to v25.0.2 for Ubuntu 23.04.
       matchFileNames: [