diff --git a/src/Type/BenevolentUnionType.php b/src/Type/BenevolentUnionType.php
index 65301394ed..6f5756662a 100644
--- a/src/Type/BenevolentUnionType.php
+++ b/src/Type/BenevolentUnionType.php
@@ -42,4 +42,13 @@ public function isAcceptedBy(Type $acceptingType, bool $strictTypes): TrinaryLog
 		return TrinaryLogic::createNo();
 	}
 
+	/**
+	 * @param callable(Type $type): TrinaryLogic $getResult
+	 * @return TrinaryLogic
+	 */
+	protected function unionResults(callable $getResult): TrinaryLogic
+	{
+		return TrinaryLogic::maxMin(...array_map($getResult, $this->getTypes()));
+	}
+
 }
diff --git a/src/Type/Php/SimpleXMLElementClassPropertyReflectionExtension.php b/src/Type/Php/SimpleXMLElementClassPropertyReflectionExtension.php
index 0b2feb187b..4278a4e2ab 100644
--- a/src/Type/Php/SimpleXMLElementClassPropertyReflectionExtension.php
+++ b/src/Type/Php/SimpleXMLElementClassPropertyReflectionExtension.php
@@ -6,6 +6,8 @@
 use PHPStan\Reflection\Php\SimpleXMLElementProperty;
 use PHPStan\Reflection\PropertiesClassReflectionExtension;
 use PHPStan\Reflection\PropertyReflection;
+use PHPStan\Type\BenevolentUnionType;
+use PHPStan\Type\NullType;
 use PHPStan\Type\ObjectType;
 
 class SimpleXMLElementClassPropertyReflectionExtension implements PropertiesClassReflectionExtension
@@ -19,7 +21,7 @@ public function hasProperty(ClassReflection $classReflection, string $propertyNa
 
 	public function getProperty(ClassReflection $classReflection, string $propertyName): PropertyReflection
 	{
-		return new SimpleXMLElementProperty($classReflection, new ObjectType('SimpleXMLElement'));
+		return new SimpleXMLElementProperty($classReflection, new BenevolentUnionType([new ObjectType('SimpleXMLElement'), new NullType()]));
 	}
 
 }
diff --git a/src/Type/UnionType.php b/src/Type/UnionType.php
index 2d20b91b6d..938340f5ef 100644
--- a/src/Type/UnionType.php
+++ b/src/Type/UnionType.php
@@ -620,7 +620,7 @@ public static function __set_state(array $properties): Type
 	 * @param callable(Type $type): TrinaryLogic $getResult
 	 * @return TrinaryLogic
 	 */
-	private function unionResults(callable $getResult): TrinaryLogic
+	protected function unionResults(callable $getResult): TrinaryLogic
 	{
 		return TrinaryLogic::extremeIdentity(...array_map($getResult, $this->types));
 	}
diff --git a/tests/PHPStan/Rules/Classes/data/impossible-instanceof.php b/tests/PHPStan/Rules/Classes/data/impossible-instanceof.php
index 0c7716dbd4..3e3bc1f9cb 100644
--- a/tests/PHPStan/Rules/Classes/data/impossible-instanceof.php
+++ b/tests/PHPStan/Rules/Classes/data/impossible-instanceof.php
@@ -375,3 +375,13 @@ public function doTest($int, $objectWithoutClass, $object, $intOrObject, $string
 		}
 	}
 }
+
+class InstanceofBenevolentUnionType
+{
+	public function doFoo(\SimpleXMLElement $xml)
+	{
+		echo $xml->branch1 instanceof \SimpleXMLElement;
+		echo $xml->branch2->branch3 instanceof \SimpleXMLElement;
+	}
+
+}