diff --git a/configure.ac b/configure.ac
index 9780991122..659ace078d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2159,7 +2159,7 @@ fi
     AC_PATH_PROG(HAVE_GETCONF_CMD, getconf, "no")
     if test "$HAVE_GETCONF_CMD" != "no"; then
         CLS=$(getconf LEVEL1_DCACHE_LINESIZE)
-        if [test "$CLS" != "" && test "$CLS" != "0"]; then
+        if [test "$CLS" != "undefined" && test "$CLS" != "" && test "$CLS" != "0"]; then
             AC_DEFINE_UNQUOTED([CLS],[${CLS}],[L1 cache line size])
         else
             AC_DEFINE([CLS],[64],[L1 cache line size])