# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
-# We have strange test case titles, so we need Autoconf 2.61 or better.
-AC_PREREQ(2.61)
+# In order for some versions of Sun Studio to compile our C++ test cases
+# correctly, we need Autoconf 2.64 or better to handle the restrict
+# keyword in at least string.h from gnulib.
+AC_PREREQ(2.64)
AC_INIT([GNU Bison],
m4_esyscmd([build-aux/git-version-gen .tarball-version]),