diff --git a/mysql-test/main/ctype_filename.result b/mysql-test/main/ctype_filename.result
index 0b214d394da..cf7d7118eb7 100644
--- a/mysql-test/main/ctype_filename.result
+++ b/mysql-test/main/ctype_filename.result
@@ -160,3 +160,18 @@ ALTER TABLE t1 CONVERT TO CHARACTER SET filename;
 ERROR 42000: Column length too big for column 'a' (max = 204); use BLOB or TEXT instead
 DROP TABLE t1;
 # End of 10.5 tests
+#
+# Start of 10.6 tests
+#
+#
+# MDEV-35393 ASAN unknown-crash in Field_varstring::reset when inserting NULL value to a table with filename charset
+#
+SET sql_mode='';
+CREATE TABLE t (a CHAR(205)) ENGINE=MYISAM CHARACTER SET filename;
+Warnings:
+Note	1246	Converting column 'a' from CHAR to VARCHAR
+INSERT INTO t VALUES (NULL);
+DROP TABLE t;
+#
+# End of 10.6 tests
+#
diff --git a/mysql-test/main/ctype_filename.test b/mysql-test/main/ctype_filename.test
index 83d1a7a5d5b..08e7269e0d3 100644
--- a/mysql-test/main/ctype_filename.test
+++ b/mysql-test/main/ctype_filename.test
@@ -167,3 +167,21 @@ ALTER TABLE t1 CONVERT TO CHARACTER SET filename;
 DROP TABLE t1;
 
 --echo # End of 10.5 tests
+
+
+--echo #
+--echo # Start of 10.6 tests
+--echo #
+
+--echo #
+--echo # MDEV-35393 ASAN unknown-crash in Field_varstring::reset when inserting NULL value to a table with filename charset
+--echo #
+
+SET sql_mode='';
+CREATE TABLE t (a CHAR(205)) ENGINE=MYISAM CHARACTER SET filename;
+INSERT INTO t VALUES (NULL);
+DROP TABLE t;
+
+--echo #
+--echo # End of 10.6 tests
+--echo #
diff --git a/mysql-test/main/ctype_filename_innodb.result b/mysql-test/main/ctype_filename_innodb.result
new file mode 100644
index 00000000000..d3535e70a3f
--- /dev/null
+++ b/mysql-test/main/ctype_filename_innodb.result
@@ -0,0 +1,18 @@
+#
+# Start of 10.6 tests
+#
+#
+# MDEV-35392 Assertion `!__asan_region_is_poisoned((vo id*) dest,templ->mysql_col_len)' failed in void row_sel_field_store_in_mysql_format_func(byte *, const mysql_row_templ_t *, const byte *, ulint)
+#
+SET sql_mode='';
+CREATE TABLE t (a CHAR(205)) ENGINE=INNODB CHARACTER SET filename;
+Warnings:
+Note	1246	Converting column 'a' from CHAR to VARCHAR
+INSERT INTO t VALUES (1);
+SELECT * FROM t;
+a
+1
+DROP TABLE t;
+#
+# End of 10.6 tests
+#
diff --git a/mysql-test/main/ctype_filename_innodb.test b/mysql-test/main/ctype_filename_innodb.test
new file mode 100644
index 00000000000..a0340919c04
--- /dev/null
+++ b/mysql-test/main/ctype_filename_innodb.test
@@ -0,0 +1,19 @@
+--source include/have_innodb.inc
+
+--echo #
+--echo # Start of 10.6 tests
+--echo #
+
+--echo #
+--echo # MDEV-35392 Assertion `!__asan_region_is_poisoned((vo id*) dest,templ->mysql_col_len)' failed in void row_sel_field_store_in_mysql_format_func(byte *, const mysql_row_templ_t *, const byte *, ulint)
+--echo #
+
+SET sql_mode='';
+CREATE TABLE t (a CHAR(205)) ENGINE=INNODB CHARACTER SET filename;
+INSERT INTO t VALUES (1);
+SELECT * FROM t;
+DROP TABLE t;
+
+--echo #
+--echo # End of 10.6 tests
+--echo #
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 45f737812e4..654fc2e93be 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -2307,6 +2307,34 @@ bool Column_definition::prepare_stage1_string(THD *thd,
                                               handler *file,
                                               ulonglong table_flags)
 {
+  if (real_field_type() == FIELD_TYPE_STRING &&
+      length*charset->mbmaxlen > 1024)
+  {
+    DBUG_ASSERT(charset->mbmaxlen > 4);
+    /*
+      Convert long CHAR columns to VARCHAR.
+      CHAR has an octet length limit of 1024 bytes.
+      The code in Binlog_type_info_fixed_string::Binlog_type_info_fixed_string
+      relies on this limit. If octet length of a CHAR column is greater
+      than 1024, then it cannot write its metadata to binlog properly.
+      In case of the filename character set with mbmaxlen=5,
+      the maximum possible character length is 1024/5=204 characters.
+      Upgrade to VARCHAR if octet length is greater than 1024.
+    */
+    char warn_buff[MYSQL_ERRMSG_SIZE];
+    if (thd->is_strict_mode())
+    {
+      my_error(ER_TOO_BIG_FIELDLENGTH, MYF(0), field_name.str,
+               static_cast<ulong>(1024 / charset->mbmaxlen));
+      return true;
+    }
+    set_handler(&type_handler_varchar);
+    my_snprintf(warn_buff, sizeof(warn_buff), ER_THD(thd, ER_AUTO_CONVERT),
+                field_name.str, "CHAR", "VARCHAR");
+    push_warning(thd, Sql_condition::WARN_LEVEL_NOTE, ER_AUTO_CONVERT,
+                 warn_buff);
+  }
+
   create_length_to_internal_length_string();
   if (prepare_blob_field(thd))
     return true;
@@ -3779,33 +3807,6 @@ bool Column_definition::prepare_blob_field(THD *thd)
 {
   DBUG_ENTER("Column_definition::prepare_blob_field");
 
-  if (real_field_type() == FIELD_TYPE_STRING && length > 1024)
-  {
-    DBUG_ASSERT(charset->mbmaxlen > 4);
-    /*
-      Convert long CHAR columns to VARCHAR.
-      CHAR has an octet length limit of 1024 bytes.
-      The code in Binlog_type_info_fixed_string::Binlog_type_info_fixed_string
-      relies on this limit. If octet length of a CHAR column is greater
-      than 1024, then it cannot write its metadata to binlog properly.
-      In case of the filename character set with mbmaxlen=5,
-      the maximum possible character length is 1024/5=204 characters.
-      Upgrade to VARCHAR if octet length is greater than 1024.
-    */
-    char warn_buff[MYSQL_ERRMSG_SIZE];
-    if (thd->is_strict_mode())
-    {
-      my_error(ER_TOO_BIG_FIELDLENGTH, MYF(0), field_name.str,
-               static_cast<ulong>(1024 / charset->mbmaxlen));
-      DBUG_RETURN(1);
-    }
-    set_handler(&type_handler_varchar);
-    my_snprintf(warn_buff, sizeof(warn_buff), ER_THD(thd, ER_AUTO_CONVERT),
-                field_name.str, "CHAR", "VARCHAR");
-    push_warning(thd, Sql_condition::WARN_LEVEL_NOTE, ER_AUTO_CONVERT,
-                 warn_buff);
-  }
-
   if (length > MAX_FIELD_VARCHARLENGTH && !(flags & BLOB_FLAG))
   {
     /* Convert long VARCHAR columns to TEXT or BLOB */