diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index 9464c344..e7257813 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -39,7 +39,7 @@ jobs:
       - name: Build spec targets
         run: |
           cd adoc
-          make OUTDIR=/tmp/out QUIET= html pdf
+          make OUTDIR=/tmp/out QUIET= COMMIT_SHA=$GITHUB_SHA html pdf
       - name: Verify reflow conformance
         run: |
           ./adoc/scripts/verify_reflow_conformance.sh
diff --git a/adoc/Makefile b/adoc/Makefile
index 97b896ef..a0086359 100644
--- a/adoc/Makefile
+++ b/adoc/Makefile
@@ -93,22 +93,14 @@ NOTEOPTS     = --attribute showtodos
 # Spell out ISO 8601 format as not all date commands support --rfc-3339
 SPECDATE     = $(shell echo `date -u "+%Y-%m-%d %TZ"`)
 
-# Generate Asciidoc attributes for spec remark
-# Could use `git log -1 --format="%cd"` to get branch commit date
-# This used to be a dependency in the spec html/pdf targets,
-# but that's likely to lead to merge conflicts. Just regenerate
-# when pushing a new spec for review to the sandbox.
-# The dependency on HEAD is per the suggestion in
-# http://neugierig.org/software/blog/2014/11/binary-revisions.html
-# Get back something clearer from the old LaTeX-based specification by
-# name the exact annotated tag. If not, list a path to the closest tag.
-SPECREMARK = from git $(shell \
-  echo `git describe --exact-match 2> /dev/null \
-        || ( git describe 2> /dev/null; echo "on branch:" ; \
-             git symbolic-ref --short HEAD 2> /dev/null \
-             || echo Git branch not available )`) \
-        commit: $(shell echo `git log -1 --format="%H" 2> /dev/null \
-                              || echo Git commit not available`)
+# Deterine the commit ID that is printed at the top of the spec.
+# In some CI systems, the build may happen outside of a git repo, so
+# "git log" may not be available.  These CI systems set the commit id via
+# "make COMMIT_SHA=...", so the build process doesn't need the "git log"
+# command.
+SPECREMARK = commit $(COMMIT_SHA)
+COMMIT_SHA = $(shell echo `git log -1 --format="%H" 2> /dev/null \
+               || echo "(not available)"`)
 
 # Some of the attributes used in building all spec documents:
 #   chapters - absolute path to chapter sources