diff --git a/storage/mroonga/ha_mroonga.cpp b/storage/mroonga/ha_mroonga.cpp
index 5db9aa0b5847d..b75ae31e70c51 100644
--- a/storage/mroonga/ha_mroonga.cpp
+++ b/storage/mroonga/ha_mroonga.cpp
@@ -776,6 +776,26 @@ static MYSQL_SYSVAR_ENUM(log_level, mrn_log_level,
                          static_cast<ulong>(mrn_log_level),
                          &mrn_log_level_typelib);
 
+static int mrn_log_file_check(THD *thd, struct st_mysql_sys_var *var,
+                              void *save, struct st_mysql_value *value)
+{
+  MRN_DBUG_ENTER_FUNCTION();
+
+  int len;
+  const char *new_value= value->val_str(value, NULL, &len);
+
+  if (!new_value || len == 0)
+  {
+    my_printf_error(ER_MRN_INVALID_NULL_VALUE_NUM,
+                    ER_MRN_INVALID_NULL_VALUE_STR, MYF(0),
+                    "mroonga_log_file");
+    DBUG_RETURN(1);
+  }
+
+  *((const char **) save)= new_value;
+
+  DBUG_RETURN(0);
+}
 static void mrn_log_file_update(THD *thd, struct st_mysql_sys_var *var,
                                 void *var_ptr, const void *save)
 {
@@ -848,7 +868,7 @@ static void mrn_log_file_update(THD *thd, struct st_mysql_sys_var *var,
 static MYSQL_SYSVAR_STR(log_file, mrn_log_file_path,
                         PLUGIN_VAR_RQCMDARG | PLUGIN_VAR_MEMALLOC,
                         "log file for " MRN_PLUGIN_NAME_STRING,
-                        NULL,
+                        mrn_log_file_check,
                         mrn_log_file_update,
                         MRN_LOG_FILE_PATH);
 
diff --git a/storage/mroonga/mysql-test/mroonga/storage/r/variable_log_file_reject_null.result b/storage/mroonga/mysql-test/mroonga/storage/r/variable_log_file_reject_null.result
new file mode 100644
index 0000000000000..c44462e7ac959
--- /dev/null
+++ b/storage/mroonga/mysql-test/mroonga/storage/r/variable_log_file_reject_null.result
@@ -0,0 +1,7 @@
+SET GLOBAL mroonga_log_file = NULL;
+ERROR HY000: NULL value can't be used for mroonga_log_file
+SET GLOBAL mroonga_log_file = '';
+ERROR HY000: NULL value can't be used for mroonga_log_file
+SHOW GLOBAL VARIABLES LIKE 'mroonga_log_file';
+Variable_name	Value
+mroonga_log_file	groonga.log
diff --git a/storage/mroonga/mysql-test/mroonga/storage/t/variable_log_file_reject_null.test b/storage/mroonga/mysql-test/mroonga/storage/t/variable_log_file_reject_null.test
new file mode 100644
index 0000000000000..f6c53f1e682da
--- /dev/null
+++ b/storage/mroonga/mysql-test/mroonga/storage/t/variable_log_file_reject_null.test
@@ -0,0 +1,30 @@
+# -*- 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/mroonga/have_mroonga.inc
+--source include/not_embedded.inc
+
+--error 16505
+SET GLOBAL mroonga_log_file = NULL;
+
+--error 16505
+SET GLOBAL mroonga_log_file = '';
+
+SHOW GLOBAL VARIABLES LIKE 'mroonga_log_file';  
+
+--source ../../include/mroonga/have_mroonga_deinit.inc