diff -urNp -x '*.orig' libguestfs-1.40.2.org/m4/guestfs-bash-completion.m4 libguestfs-1.40.2/m4/guestfs-bash-completion.m4
--- libguestfs-1.40.2.org/m4/guestfs-bash-completion.m4	2019-02-07 15:45:56.974956261 +0100
+++ libguestfs-1.40.2/m4/guestfs-bash-completion.m4	2021-03-30 23:04:13.624972254 +0200
@@ -16,6 +16,11 @@
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
 dnl Bash completion.
+AC_ARG_WITH([completionsdir], [AS_HELP_STRING([--with-completionsdir], [path to bash completion directory])], [
+    bash_completion=yes
+    BASH_COMPLETIONS_DIR=$withval
+    AC_SUBST([BASH_COMPLETIONS_DIR])
+],[
 PKG_CHECK_MODULES([BASH_COMPLETION], [bash-completion >= 2.0], [
     bash_completion=yes
     AC_MSG_CHECKING([for bash-completions directory])
@@ -26,4 +31,5 @@ PKG_CHECK_MODULES([BASH_COMPLETION], [ba
     bash_completion=no
     AC_MSG_WARN([bash-completion not installed])
 ])
+])
 AM_CONDITIONAL([HAVE_BASH_COMPLETION],[test "x$bash_completion" = "xyes"])