diff --git a/tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php b/tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php
index 80b4e8ee120..e86dd797009 100644
--- a/tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php
+++ b/tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php
@@ -561,6 +561,14 @@ public function testArrayFunctionCallbackIsValidated(): void
 				'Parameter #2 $callback of function array_reduce expects callable(string, int|string): string, Closure(string, string): string given.',
 				5,
 			],
+			[
+				'Parameter #2 $callback of function array_reduce expects callable(string|null, int): string|null, Closure(string, int): string given.',
+				11
+			],
+			[
+				'Parameter #2 $callback of function array_reduce expects callable(string|null, int): string|null, Closure(string, int): string given.',
+				18
+			]
 		]);
 
 		$this->analyse([__DIR__ . '/data/array_map.php'], [
diff --git a/tests/PHPStan/Rules/Functions/data/array_reduce.php b/tests/PHPStan/Rules/Functions/data/array_reduce.php
index da95486054f..2857029bd31 100644
--- a/tests/PHPStan/Rules/Functions/data/array_reduce.php
+++ b/tests/PHPStan/Rules/Functions/data/array_reduce.php
@@ -5,3 +5,15 @@
 	fn(string $foo, string $current): string => $foo . $current,
 	''
 );
+
+array_reduce(
+	[1,2,3],
+	fn(string $foo, int $current): string => $foo . $current,
+	null
+);
+
+
+array_reduce(
+	[1,2,3],
+	fn(string $foo, int $current): string => $foo . $current,
+);