diff --git a/configure.ac b/configure.ac
index 469df07..edb692d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -93,7 +93,7 @@ AM_CONDITIONAL([HAVE_VFORK],[test "x$ac_cv_func_vfork_works" = xyes])
 AC_CONFIG_FILES([Makefile src/Makefile tests/Makefile])
 AC_OUTPUT
 
-if test x"$ac_cv_tls" != x"none"; then
+if test x"$ac_cv_tls" = x"none"; then
     AC_MSG_WARN([thread-local storage not supported by compiler, \
 possible race condition in threaded programs])
 fi