diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 55ed35c..34754e2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -7,7 +7,11 @@ on:
 
 jobs:
   test:
-    runs-on: ubuntu-latest
+    # A named image rather than `ubuntu-latest`: that label moves to the next
+    # Ubuntu on a date GitHub picks, and with it the system libraries Playwright
+    # installs for Chromium. Which image the tests run on is a decision to make
+    # here, not one to be made by a calendar.
+    runs-on: ubuntu-24.04
 
     steps:
       - uses: actions/checkout@v7
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 3fe1013..9d68ccb 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -7,7 +7,9 @@ on:
 
 jobs:
   publish:
-    runs-on: ubuntu-latest
+    # Pinned for the same reason as in ci.yml: a release must not be the first
+    # run to find out that the image moved.
+    runs-on: ubuntu-24.04
 
     permissions:
       # Creating the release page.