diff --git a/storage/mroonga/ha_mroonga.cpp b/storage/mroonga/ha_mroonga.cpp
index 3a85eaf18cd50..5db9aa0b5847d 100644
--- a/storage/mroonga/ha_mroonga.cpp
+++ b/storage/mroonga/ha_mroonga.cpp
@@ -938,6 +938,12 @@ static void mrn_default_tokenizer_update(THD *thd, struct st_mysql_sys_var *var,
   char **old_value_ptr = (char **)var_ptr;
   grn_ctx *ctx = &mrn_ctx;
 
+  if(!new_value) {
+    new_value = "off";
+#ifndef MRN_NEED_FREE_STRING_MEMALLOC_PLUGIN_VAR
+    new_value = mrn_my_strdup(new_value, MYF(MY_WME));
+#endif
+  }
   mrn_change_encoding(ctx, system_charset_info);
   if (strcmp(*old_value_ptr, new_value) == 0) {
     GRN_LOG(ctx, GRN_LOG_NOTICE,
diff --git a/storage/mroonga/mysql-test/mroonga/storage/r/variable_default_tokenizer_disable.result b/storage/mroonga/mysql-test/mroonga/storage/r/variable_default_tokenizer_disable.result
new file mode 100644
index 0000000000000..45f1c7adddf39
--- /dev/null
+++ b/storage/mroonga/mysql-test/mroonga/storage/r/variable_default_tokenizer_disable.result
@@ -0,0 +1,5 @@
+SET GLOBAL mroonga_default_tokenizer = NULL;
+SHOW GLOBAL VARIABLES LIKE 'mroonga_default_tokenizer';
+Variable_name	Value
+mroonga_default_tokenizer	off
+SET GLOBAL mroonga_default_tokenizer = DEFAULT;
diff --git a/storage/mroonga/mysql-test/mroonga/storage/t/variable_default_tokenizer_disable.test b/storage/mroonga/mysql-test/mroonga/storage/t/variable_default_tokenizer_disable.test
new file mode 100644
index 0000000000000..63df372f3faae
--- /dev/null
+++ b/storage/mroonga/mysql-test/mroonga/storage/t/variable_default_tokenizer_disable.test
@@ -0,0 +1,25 @@
+# -*- mode: sql; sql-product: mysql -*-
+#
+# Copyright (C) 2026  hadeer <hadderramadan7@gmail.com>
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+--source include/not_embedded.inc
+--source ../../include/mroonga/have_mroonga.inc
+
+SET GLOBAL mroonga_default_tokenizer = NULL;
+SHOW GLOBAL VARIABLES LIKE 'mroonga_default_tokenizer';
+SET GLOBAL mroonga_default_tokenizer = DEFAULT;
+
+--source ../../include/mroonga/have_mroonga_deinit.inc