diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index d662e0d9..52dad3c9 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -26,9 +26,10 @@ jobs:
     runs-on: ubuntu-latest
 
     # Use the Khronos container with the asciidoctor toolchain preinstalled.  We
-    # reference the image by both its SHA and its tag because they sometimes
-    # overwrite a tag with a different image (which has a different SHA).
-    container: khronosgroup/docker-images:asciidoctor-spec.20240630@sha256:bd30a83285a2ea062598f053b5bd8ebc843e16c639c0e4cd88ab4bbb4e63ead3
+    # reference the image its SHA rather than its tag because they sometimes
+    # overwrite a tag with a different image (which has a different SHA).  This
+    # SHA corresponds to tag "asciidoctor-spec.20240630".
+    container: khronosgroup/docker-images@sha256:bd30a83285a2ea062598f053b5bd8ebc843e16c639c0e4cd88ab4bbb4e63ead3
 
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it