diff --git a/patches/pkgbuild/libassuan.sh b/patches/pkgbuild/libassuan.sh
new file mode 100755
index 0000000..daae3ab
--- /dev/null
+++ b/patches/pkgbuild/libassuan.sh
@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+# libassuan: fetch from the GitHub mirror instead of dev.gnupg.org.
+#
+#   fatal: unable to access 'https://dev.gnupg.org/source/libassuan.git/'
+#
+# This is NOT a port problem. dev.gnupg.org is simply unreachable from this
+# build host -- measured: HTTP 000, while github.com/gpg/libassuan.git and
+# gnupg.org/ftp both answer. The GnuPG project publishes the same history to
+# GitHub, so the mirror is the upstream content, not a third-party copy.
+#
+# The commit the PKGBUILD pins is untouched: only the transport changes, so
+# what gets built is bit-for-bit what Arch specifies.
+set -euo pipefail
+sed -i 's|https://dev\.gnupg\.org/source/libassuan\.git|https://github.com/gpg/libassuan.git|' PKGBUILD
+grep -q 'dev.gnupg.org' PKGBUILD && { echo "libassuan: dev.gnupg.org still referenced" >&2; exit 1; }
+grep -m1 'github.com/gpg/libassuan' PKGBUILD | sed 's/^\s*//'
+echo "libassuan: source switched to the GitHub mirror (dev.gnupg.org unreachable here)"
diff --git a/scripts/bootstrap-pacman.sh b/scripts/bootstrap-pacman.sh
index 06a2d51..31325ba 100755
--- a/scripts/bootstrap-pacman.sh
+++ b/scripts/bootstrap-pacman.sh
@@ -74,6 +74,19 @@ configure_makepkg() {
     # pacman refuses to initialise alpm without its database directory. The
     # error is only a warning during packaging, but it hides real ones.
     sudo mkdir -p /var/lib/pacman
+    # CHOST must be the CANONICAL triplet, not the Debian-style one.
+    #
+    # gcc -dumpmachine reports s390x-linux-gnu here, but config.sub
+    # canonicalises that to s390x-ibm-linux-gnu, and GCC builds its tree
+    # under the canonical name. Arch PKGBUILDs assume the canonical form --
+    # theirs is x86_64-pc-linux-gnu, with the vendor field present -- so
+    # gcc's own PKGBUILD looked for $CHOST/libstdc++-v3/doc and found
+    # nothing:
+    #
+    #   make: *** s390x-linux-gnu/libstdc++-v3/doc: No such file or directory
+    #
+    # while the build had created s390x-ibm-linux-gnu/libstdc++-v3/doc.
+    sudo sed -i 's|^CHOST=.*|CHOST="s390x-ibm-linux-gnu"|' /etc/makepkg.conf
     grep -E '^(CARCH|CHOST|MAKEFLAGS)=' /etc/makepkg.conf
 }