diff --git a/application/Espo/Core/Utils/Database/DBAL/FieldTypes/JsonArrayType.php b/application/Espo/Core/Utils/Database/DBAL/FieldTypes/JsonArrayType.php
index ef95c66742..6e22fd69fc 100644
--- a/application/Espo/Core/Utils/Database/DBAL/FieldTypes/JsonArrayType.php
+++ b/application/Espo/Core/Utils/Database/DBAL/FieldTypes/JsonArrayType.php
@@ -29,7 +29,7 @@
 
 namespace Espo\Core\Utils\Database\DBAL\FieldTypes;
 
-class JsonArrayType extends \Doctrine\DBAL\Types\JsonArrayType
+class JsonArrayType extends \Doctrine\DBAL\Types\TextType
 {
     const JSON_ARRAY = 'jsonArray';
 
diff --git a/application/Espo/Core/Utils/Database/DBAL/FieldTypes/JsonObjectType.php b/application/Espo/Core/Utils/Database/DBAL/FieldTypes/JsonObjectType.php
index a5ecc48037..d2eee31b80 100644
--- a/application/Espo/Core/Utils/Database/DBAL/FieldTypes/JsonObjectType.php
+++ b/application/Espo/Core/Utils/Database/DBAL/FieldTypes/JsonObjectType.php
@@ -29,7 +29,7 @@
 
 namespace Espo\Core\Utils\Database\DBAL\FieldTypes;
 
-class JsonObjectType extends \Doctrine\DBAL\Types\ObjectType
+class JsonObjectType extends \Doctrine\DBAL\Types\TextType
 {
     const JSON_OBJECT = 'jsonObject';
 
diff --git a/application/Espo/Core/Utils/Database/DBAL/Platforms/MySqlPlatform.php b/application/Espo/Core/Utils/Database/DBAL/Platforms/MySqlPlatform.php
index de81cfc6b9..6c7ae64684 100644
--- a/application/Espo/Core/Utils/Database/DBAL/Platforms/MySqlPlatform.php
+++ b/application/Espo/Core/Utils/Database/DBAL/Platforms/MySqlPlatform.php
@@ -38,6 +38,10 @@ use Doctrine\DBAL\Schema\Column;
 
 class MySqlPlatform extends \Doctrine\DBAL\Platforms\MySqlPlatform
 {
+    /* Espo */
+    const LENGTH_LIMIT_LONGTEXT = 4294967295;
+    /* Espo: end */
+
     public function getAlterTableSQL(TableDiff $diff)
     {
         $columnSql = array();
@@ -453,6 +457,29 @@ class MySqlPlatform extends \Doctrine\DBAL\Platforms\MySqlPlatform
         return 'MEDIUMTEXT';
     }
 
+    /* Espo: fix a problem of changing text field type */
+    public function getClobTypeLength($type)
+    {
+        switch ($type) {
+            case 'tinytext':
+                return static::LENGTH_LIMIT_TINYTEXT;
+                break;
+
+            case 'text':
+                return static::LENGTH_LIMIT_TEXT;
+                break;
+
+            case 'mediumtext':
+                return static::LENGTH_LIMIT_MEDIUMTEXT;
+                break;
+
+            case 'longtext':
+                return static::LENGTH_LIMIT_LONGTEXT;
+                break;
+        }
+    }
+    /* Espo: end */
+
     public function getColumnDeclarationListSQL(array $fields)
     {
         $queryFields = array();
diff --git a/application/Espo/Core/Utils/Database/DBAL/Schema/MySqlSchemaManager.php b/application/Espo/Core/Utils/Database/DBAL/Schema/MySqlSchemaManager.php
index c50495af53..660502e8a7 100644
--- a/application/Espo/Core/Utils/Database/DBAL/Schema/MySqlSchemaManager.php
+++ b/application/Espo/Core/Utils/Database/DBAL/Schema/MySqlSchemaManager.php
@@ -203,6 +203,15 @@ class MySqlSchemaManager extends \Doctrine\DBAL\Schema\MySqlSchemaManager
             case 'year':
                 $length = null;
                 break;
+
+            /* Espo: fix a problem of changing text field type */
+            case 'tinytext':
+            case 'text':
+            case 'mediumtext':
+            case 'longtext':
+                $length = $this->_platform->getClobTypeLength($dbType);
+                break;
+            /* Espo: end */
         }
 
         $length = ((int) $length == 0) ? null : (int) $length;