diff --git a/acinclude.m4 b/acinclude.m4
index 6fc862d5b2..e581d9bb70 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -455,7 +455,7 @@ case $system in
                 case "$GUESS_LINUX_VERSION" in
                   2.2.*) AFS_SYSKVERS=22 ;;
                   2.4.*) AFS_SYSKVERS=24 ;;
-                  2.6.* | 3.*) AFS_SYSKVERS=26 ;;
+                  [2.6.* | [3-9]* | [1-2][0-9]*]) AFS_SYSKVERS=26 ;;
                   *) AC_MSG_ERROR(Couldn't guess your Linux version [2]) ;;
                 esac
                 ;;