diff --git a/configure.ac b/configure.ac
index 433fe9f..f2ea0f3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,4 +1,4 @@
-AC_PREREQ(2.64)
+AC_PREREQ(2.63)
 
 AC_INIT([protobuf-c],
         [1.2.1],