--- a/acinclude.m4
+++ b/acinclude.m4
@@ -894,6 +894,8 @@ changequote(, )dnl
             x2.[23456789]* ) ;;
 changequote(, )dnl
             x3.* ) ;;
+changequote(, )dnl
+            x4.* ) ;;
 changequote([, ])
             * ) braindead=yes ;;
         esac