diff --git a/docs/en/reference/custom-mapping-types.rst b/docs/en/reference/custom-mapping-types.rst
index 8e9ffad5d..cd1a11ac0 100644
--- a/docs/en/reference/custom-mapping-types.rst
+++ b/docs/en/reference/custom-mapping-types.rst
@@ -31,7 +31,7 @@ a ``DateTimeImmutable``.
         // This trait provides default closureToPHP used during data hydration
         use ClosureToPHP;
 
-        public function convertToPHPValue($value): ?DateTimeImmutable
+        public function convertToPHPValue($value): DateTimeImmutable
         {
             $timeZone = new DateTimeZone($value['tz']);
             $dateTime = $value['utc']
@@ -41,7 +41,7 @@ a ``DateTimeImmutable``.
             return DateTimeImmutable::createFromMutable($dateTime);
         }
 
-        public function convertToDatabaseValue($value): ?array
+        public function convertToDatabaseValue($value): array
         {
             return [
                 'utc' => new UTCDateTime($value),
diff --git a/tests/Documentation/CustomMapping/DateTimeWithTimezoneType.php b/tests/Documentation/CustomMapping/DateTimeWithTimezoneType.php
index 4bad52e55..429b837d8 100644
--- a/tests/Documentation/CustomMapping/DateTimeWithTimezoneType.php
+++ b/tests/Documentation/CustomMapping/DateTimeWithTimezoneType.php
@@ -5,6 +5,7 @@
 namespace Documentation\CustomMapping;
 
 use DateTimeImmutable;
+use DateTimeInterface;
 use DateTimeZone;
 use Doctrine\ODM\MongoDB\Types\ClosureToPHP;
 use Doctrine\ODM\MongoDB\Types\Type;
@@ -15,7 +16,8 @@ class DateTimeWithTimezoneType extends Type
     // This trait provides default closureToPHP used during data hydration
     use ClosureToPHP;
 
-    public function convertToPHPValue($value): ?DateTimeImmutable
+    /** @param array{utc: UTCDateTime, tz: string} $value */
+    public function convertToPHPValue($value): DateTimeImmutable
     {
         $timeZone = new DateTimeZone($value['tz']);
         $dateTime = $value['utc']
@@ -25,7 +27,12 @@ public function convertToPHPValue($value): ?DateTimeImmutable
         return DateTimeImmutable::createFromMutable($dateTime);
     }
 
-    public function convertToDatabaseValue($value): ?array
+    /**
+     * @param DateTimeInterface $value
+     *
+     * @return array{utc: UTCDateTime, tz: string}
+     */
+    public function convertToDatabaseValue($value): array
     {
         return [
             'utc' => new UTCDateTime($value),