diff --git a/.github/workflows/check-error-docs.yml b/.github/workflows/check-error-docs.yml
index 53e7e9644e..8f782f6aa8 100644
--- a/.github/workflows/check-error-docs.yml
+++ b/.github/workflows/check-error-docs.yml
@@ -28,8 +28,10 @@ jobs:
       - name: JS configure
         run: cd website && yarn install --production
 
-      - name: check
+      - name: check docs
         run: node website/check-error-documentation.mjs
+      - name: check diagnostics
+        run: node website/check-diagnostic-messages.mjs
 
 # quick-lint-js finds bugs in JavaScript programs.
 # Copyright (C) 2020  Matthew Glazar