diff --git a/configure.ac b/configure.ac
index fc8ac4bd..0165c5e9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -7,6 +7,7 @@ AM_CONFIG_HEADER(config.h)
 AM_MAINTAINER_MODE
 AM_INIT_AUTOMAKE(c-ares, CVS)
 
+AC_AIX
 AC_PROG_CC
 AC_PROG_INSTALL