diff --git a/bootstrap.conf b/bootstrap.conf
index 5685ad55b..8289f693a 100644
--- a/bootstrap.conf
+++ b/bootstrap.conf
@@ -105,6 +105,10 @@ gnulib_modules="
 	xstrtol xstrtold xstrtoumax yesno
 "
 
+# Required at least for truncate's truncate-fail-diag test
+# on Solaris 7, Solaris 9, and HP-UX 11.
+gnulib_modules="$gnulib_modules open"
+
 # Other locale categories that need message catalogs.
 EXTRA_LOCALE_CATEGORIES=LC_TIME