diff --git a/unix/configure.ac b/unix/configure.ac
index 058218d..dd2b633 100644
--- a/unix/configure.ac
+++ b/unix/configure.ac
@@ -1,5 +1,5 @@
 dnl Process this file with autoconf to produce a configure script.
-AC_PREREQ([2.61])
+AC_PREREQ([2.57])
 AC_INIT([tigervnc], [0.0.90], [http://www.tigervnc.org])
 AM_INIT_AUTOMAKE([-Wall foreign dist-bzip2])