diff --git a/configure.in b/configure.in
index 6d0935a35..93b3b395d 100644
--- a/configure.in
+++ b/configure.in
@@ -15,6 +15,9 @@ case "$host" in
 *-*-sunos4*)
 	AC_DEFINE(SunOS, 4)
 	;;
+*-*-solaris2*)
+	AC_DEFINE(SunOS, 5)
+	;;
 esac
 
 dnl Checks for programs.