diff --git a/configure.ac b/configure.ac
index 8980b4f..ff8c793 100644
--- a/configure.ac
+++ b/configure.ac
@@ -24,7 +24,7 @@ dnl OF THIS SOFTWARE.
 
 dnl Process this file with autoconf to produce a configure script.
 
-AC_PREREQ(2.64)
+AC_PREREQ(2.63)
 AC_INIT([LibTIFF Software],[3.9.5],[tiff@lists.maptools.org],[tiff])
 AC_CONFIG_AUX_DIR(config)
 AC_CONFIG_MACRO_DIR(m4)