diff --git a/src/TypeConverter/TimestampTypeConverter.php b/src/TypeConverter/TimestampTypeConverter.php
index 8e547b3..260406c 100644
--- a/src/TypeConverter/TimestampTypeConverter.php
+++ b/src/TypeConverter/TimestampTypeConverter.php
@@ -21,6 +21,7 @@
 use Sunrise\Hydrator\AnnotationReaderAwareInterface;
 use Sunrise\Hydrator\AnnotationReaderInterface;
 use Sunrise\Hydrator\Dictionary\ContextKey;
+use Sunrise\Hydrator\Exception\InvalidObjectException;
 use Sunrise\Hydrator\Exception\InvalidValueException;
 use Sunrise\Hydrator\Type;
 use Sunrise\Hydrator\TypeConverterInterface;
@@ -34,6 +35,7 @@
 
 use const FILTER_NULL_ON_FAILURE;
 use const FILTER_VALIDATE_INT;
+use const PHP_MAJOR_VERSION;
 
 /**
  * @since 3.1.0
@@ -76,6 +78,11 @@ public function castValue($value, Type $type, array $path, array $context): Gene
             return;
         }
 
+        // The DateTimeImmutable::createFromFormat method returns self instead of static...
+        if (PHP_MAJOR_VERSION === 7 && $className !== DateTimeImmutable::class) {
+            throw InvalidObjectException::unsupportedType($type);
+        }
+
         // phpcs:ignore Generic.Files.LineLength
         $format = $this->annotationReader->getAnnotations(Format::class, $type->getHolder())->current()->value ?? $context[ContextKey::TIMESTAMP_FORMAT] ?? self::DEFAULT_FORMAT;
 
@@ -110,14 +117,14 @@ public function castValue($value, Type $type, array $path, array $context): Gene
             throw InvalidValueException::mustBeString($path);
         }
 
-        /** @var int|string $value */
+        $value = (string) $value;
 
         $timezone = null;
         if (isset($context[ContextKey::TIMEZONE])) {
             $timezone = new DateTimeZone($context[ContextKey::TIMEZONE]);
         }
 
-        $timestamp = $className::createFromFormat($format, (string) $value, $timezone);
+        $timestamp = $className::createFromFormat($format, $value, $timezone);
         if ($timestamp === false) {
             throw InvalidValueException::invalidTimestamp($path, $format);
         }
diff --git a/tests/HydratorTest.php b/tests/HydratorTest.php
index 49f24fe..dbf4e5b 100644
--- a/tests/HydratorTest.php
+++ b/tests/HydratorTest.php
@@ -1864,6 +1864,8 @@ public function testHydrateTimestampPropertyWithoutValue(): void
     // phpcs:ignore Generic.Files.LineLength
     public function testHydrateOverriddenDateTimeImmutable(array $data, string $expected, ?string $format = null, ?string $timezone = null): void
     {
+        $this->phpRequired('8.0');
+
         $object = new class {
             public Fixture\OverriddenDateTimeImmutable $value;
         };