diff --git a/configure.ac b/configure.ac
index 0807f012..82a27f14 100644
--- a/configure.ac
+++ b/configure.ac
@@ -29,7 +29,7 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-AC_PREREQ([2.56])
+AC_PREREQ([2.68])
 AC_CONFIG_MACRO_DIRS([m4])
 sinclude(./m4/acx_openssl.m4)
 sinclude(./m4/acx_getaddrinfo.m4)