diff --git a/bacula/autoconf/bacula-macros/db.m4 b/bacula/autoconf/bacula-macros/db.m4
index 6ca82a0..4e9007d 100644
--- a/bacula/autoconf/bacula-macros/db.m4
+++ b/bacula/autoconf/bacula-macros/db.m4
@@ -485,6 +485,7 @@ AC_HELP_STRING([--with-mysql@<:@=DIR@:>@], [Include MySQL support. DIR is the My
            DB_LIBS="${DB_LIBS} ${MYSQL_LIBS}"
            MYSQL_LIBS="$MYSQL_LIBDIR"
            MYSQL_INCLUDE="$MYSQL_INCDIR"
+           AC_DEFINE(HAVE_MYSQL_THREAD_SAFE, 1, [Set if have mysql_thread_safe])
            if test -z "${batch_insert_db_backends}"; then
               batch_insert_db_backends="MySQL"
            else