diff --git a/UPGRADE.md b/UPGRADE.md
index e6730319b00..e1335b1441d 100644
--- a/UPGRADE.md
+++ b/UPGRADE.md
@@ -1,5 +1,9 @@
 # Upgrade to 2.9
 
+## Deprecated `Doctrine\DBAL\Types\Type::__toString()`
+
+Relying on string representation is discouraged and will be removed in DBAL 3.0.
+
 ## Deprecated `NULL` value of `$offset` in LIMIT queries
 
 The `NULL` value of the `$offset` argument in `AbstractPlatform::(do)?ModifyLimitQuery()` methods is deprecated. If explicitly used in the method call, the absence of the offset should be indicated with a `0`.
diff --git a/lib/Doctrine/DBAL/Types/Type.php b/lib/Doctrine/DBAL/Types/Type.php
index 453631e0aaa..56405dfe909 100644
--- a/lib/Doctrine/DBAL/Types/Type.php
+++ b/lib/Doctrine/DBAL/Types/Type.php
@@ -274,6 +274,8 @@ public static function getTypesMap()
 
     /**
      * @return string
+     *
+     * @deprecated Relying on string representation is discouraged and will be removed in DBAL 3.0.
      */
     public function __toString()
     {