diff --git a/patches/pkgbuild/grep.sh b/patches/pkgbuild/grep.sh
index 532612f..e35dc3b 100755
--- a/patches/pkgbuild/grep.sh
+++ b/patches/pkgbuild/grep.sh
@@ -1,36 +1,41 @@
 #!/usr/bin/env bash
-# grep: neutralise the pkg.m4 serial check inside its own bootstrap script.
+# grep: neutralise the pkg.m4 serial check inside bootstrap.conf.
 #
 #   ./bootstrap: do not use pkg.m4 serial 12;
 #   see https://lists.gnu.org/r/grep-devel/2025-04/msg00006.html
 #
 # grep is the only package here that INSPECTS the version of the m4 macros
-# its build host provides. This is not an s390x incompatibility: the same
-# refusal happens on any Ubuntu host, x86 included.
+# its build host provides. Not an s390x incompatibility: the same refusal
+# happens on any Ubuntu host, x86 included -- pkg-config 0.29.2 ships that
+# serial everywhere.
 #
-# A PREVIOUS VERSION of this hook skipped ./bootstrap entirely, on the
-# assumption that the source was a released tarball and therefore already
-# bootstrapped. It is not -- it is a git checkout, so skipping bootstrap
-# removed configure itself:
+# TWO EARLIER VERSIONS OF THIS HOOK WERE WRONG, both for the same reason --
+# assuming the shape of a file instead of reading it:
 #
-#   PKGBUILD: line 43: ./configure: No such file or directory
+#   1. Skipping ./bootstrap. The source is a git checkout, not a released
+#      tarball, so that removed configure itself:
+#        PKGBUILD: line 43: ./configure: No such file or directory
+#   2. Editing `bootstrap`. The check is not there. It lives in
+#      bootstrap.conf, in a shell function, built from a $url variable --
+#      which is why grepping for the literal message found nothing.
 #
-# The check itself is what has to go, and it lives in the extracted source,
-# so it is removed from prepare() rather than from the PKGBUILD directly.
+# The check is two lines: a grep for the serial, and a die. Replaced by a
+# no-op that keeps the surrounding function valid.
 set -euo pipefail
 python3 - <<'PY'
 import io, re
 s = io.open("PKGBUILD", encoding="utf-8").read()
-fix = """  # Port: drop bootstrap's host m4 vetting; see patches/pkgbuild/grep.sh
-  sed -i '/do not use pkg.m4 serial/,+1d' bootstrap
+fix = """  # Port: bootstrap.conf refuses the host pkg.m4 serial; see
+  # patches/pkgbuild/grep.sh. The check spans two lines, ending in "|| :".
+  sed -i "/serial 12. m4.pkg.m4/,+1c\\\\  :" bootstrap.conf
 """
 m = re.search(r"\nprepare\(\) \{\n(\s*cd [^\n]*\n)", s)
 assert m, "prepare() with a cd not found"
 s = s[:m.end()] + fix + s[m.end():]
 io.open("PKGBUILD", "w", encoding="utf-8").write(s)
 PY
-grep -q "drop bootstrap's host m4 vetting" PKGBUILD || {
-    echo "grep: m4 check removal not inserted" >&2; exit 1; }
+grep -q 'bootstrap.conf refuses the host pkg.m4' PKGBUILD || {
+    echo "grep: patch step not inserted" >&2; exit 1; }
 grep -qE '^\s*\./bootstrap' PKGBUILD || {
-    echo "grep: bootstrap is no longer invoked -- configure would be missing" >&2; exit 1; }
-echo "grep: bootstrap kept, its pkg.m4 serial check neutralised"
+    echo "grep: bootstrap no longer invoked -- configure would be missing" >&2; exit 1; }
+echo "grep: bootstrap kept, its bootstrap.conf serial check neutralised"