diff --git a/contrib/guix/libexec/build.sh b/contrib/guix/libexec/build.sh
index c49553bec3..a4a17cf110 100755
--- a/contrib/guix/libexec/build.sh
+++ b/contrib/guix/libexec/build.sh
@@ -205,7 +205,8 @@ GIT_ARCHIVE="${DIST_ARCHIVE_BASE}/${DISTNAME}.tar.gz"
 # Create the source tarball if not already there
 if [ ! -e "$GIT_ARCHIVE" ]; then
     mkdir -p "$(dirname "$GIT_ARCHIVE")"
-    git archive --prefix="${DISTNAME}/" --output="$GIT_ARCHIVE" HEAD
+    CONFIG_SITE="${BASEPREFIX}/${HOST}/share/config.site" \
+    contrib/guix/libexec/make_release_tarball.sh "${GIT_ARCHIVE}" "${DISTNAME}"
 fi
 
 mkdir -p "$OUTDIR"
@@ -248,8 +249,6 @@ mkdir -p "$DISTSRC"
     # Extract the source tarball
     tar --strip-components=1 -xf "${GIT_ARCHIVE}"
 
-    ./autogen.sh
-
     # Configure this DISTSRC for $HOST
     # shellcheck disable=SC2086
     env CONFIG_SITE="${BASEPREFIX}/${HOST}/share/config.site" \
diff --git a/contrib/guix/libexec/make_release_tarball.sh b/contrib/guix/libexec/make_release_tarball.sh
new file mode 100755
index 0000000000..c99e6fb500
--- /dev/null
+++ b/contrib/guix/libexec/make_release_tarball.sh
@@ -0,0 +1,41 @@
+#!/bin/sh
+# Copyright (c) 2020 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+#
+# A helper script to generate source release tarball
+
+export LC_ALL=C
+set -ex
+
+[ "$#" -ge 2 ]
+
+GIT_ARCHIVE="$1"
+DISTNAME="$2"
+
+git archive --prefix="${DISTNAME}/" HEAD | tar -xp
+
+# Generate correct build info file from git, before we lose git
+GIT_BUILD_INFO="$(share/genbuild.sh /dev/stdout)"
+sed 's/\/\/ No build information available/'"${GIT_BUILD_INFO}"'/' -i "${DISTNAME}/share/genbuild.sh"
+
+cd "${DISTNAME}"
+
+./autogen.sh
+./configure --prefix=/ --disable-ccache --disable-maintainer-mode --disable-dependency-tracking
+make distclean
+
+cd ..
+tar \
+  --format=ustar \
+  --exclude autom4te.cache \
+  --exclude .deps \
+  --exclude .git \
+  --sort=name \
+  --mode='u+rw,go+r-w,a+X' --owner=0 --group=0 \
+  --mtime="${REFERENCE_DATETIME}" \
+  -c "${DISTNAME}" | \
+  gzip -9n \
+  >"${GIT_ARCHIVE}"
+
+rm -rf "${DISTNAME}"
diff --git a/share/genbuild.sh b/share/genbuild.sh
index ecc96160e6..963113ae2c 100755
--- a/share/genbuild.sh
+++ b/share/genbuild.sh
@@ -18,9 +18,14 @@ else
     exit 1
 fi
 
+# This checks that we are actually part of the intended git repository, and not just getting info about some unrelated git repository that the code happens to be in a directory under
+git_check_in_repo() {
+    ! { git status --porcelain -uall --ignored "$@" 2>/dev/null || echo '??'; } | grep -q '?'
+}
+
 GIT_TAG=""
 GIT_COMMIT=""
-if [ "${BITCOIN_GENBUILD_NO_GIT}" != "1" ] && [ -e "$(command -v git)" ] && [ "$(git rev-parse --is-inside-work-tree 2>/dev/null)" = "true" ]; then
+if [ "${BITCOIN_GENBUILD_NO_GIT}" != "1" ] && [ -e "$(command -v git)" ] && [ "$(git rev-parse --is-inside-work-tree 2>/dev/null)" = "true" ] && git_check_in_repo share/genbuild.sh; then
     # clean 'dirty' status of touched files that haven't been modified
     git diff >/dev/null 2>/dev/null
 
@@ -40,7 +45,9 @@ if [ -n "$GIT_TAG" ]; then
 elif [ -n "$GIT_COMMIT" ]; then
     NEWINFO="#define BUILD_GIT_COMMIT \"$GIT_COMMIT\""
 else
-    NEWINFO="// No build information available"
+    # NOTE: The NEWINFO line below this comment gets replaced by a string-match in contrib/guix/libexec/make_release_tarball.sh
+    # If changing it, update the script too!
+    NEWINFO='// No build information available'
 fi
 
 # only update build.h if necessary