diff --git a/build/PHPStan/Build/RequiredPhpVersionVisitor.php b/build/PHPStan/Build/RequiredPhpVersionVisitor.php
index 3103d6f725..9af2e885a4 100644
--- a/build/PHPStan/Build/RequiredPhpVersionVisitor.php
+++ b/build/PHPStan/Build/RequiredPhpVersionVisitor.php
@@ -67,6 +67,7 @@ public function enterNode(Node $node): ?Node
 		}
 
 		if ($node instanceof Node\UnionType) {
+			$this->require(self::PHP_8_0, 'union types', $node);
 			foreach ($node->types as $innerType) {
 				if ($innerType instanceof Node\IntersectionType) {
 					$this->require(self::PHP_8_2, 'disjunctive normal form types', $innerType);
diff --git a/tests/PHPStan/Analyser/data/bug-9860.php b/tests/PHPStan/Analyser/data/bug-9860.php
index d3702fed7a..1853527ed6 100644
--- a/tests/PHPStan/Analyser/data/bug-9860.php
+++ b/tests/PHPStan/Analyser/data/bug-9860.php
@@ -1,4 +1,4 @@
-<?php declare(strict_types = 1);
+<?php declare(strict_types = 1); // lint >= 8.0
 
 namespace Bug9860;
 
diff --git a/tests/PHPStan/Analyser/nsrt/bug-11703.php b/tests/PHPStan/Analyser/nsrt/bug-11703.php
index ae1a91127b..ec2f07fbcf 100644
--- a/tests/PHPStan/Analyser/nsrt/bug-11703.php
+++ b/tests/PHPStan/Analyser/nsrt/bug-11703.php
@@ -1,5 +1,5 @@
-<?php declare(strict_types = 1);
-
+<?php // lint >= 8.0
+declare(strict_types = 1);
 namespace Bug11703;
 
 use function PHPStan\Testing\assertType;
diff --git a/tests/PHPStan/Analyser/nsrt/bug-12125.php b/tests/PHPStan/Analyser/nsrt/bug-12125.php
index 815e3cb701..c7dc37ad9c 100644
--- a/tests/PHPStan/Analyser/nsrt/bug-12125.php
+++ b/tests/PHPStan/Analyser/nsrt/bug-12125.php
@@ -1,5 +1,5 @@
-<?php declare(strict_types = 1);
-
+<?php // lint >= 8.0
+declare(strict_types = 1);
 namespace Bug12125;
 
 use ArrayAccess;
diff --git a/tests/PHPStan/Analyser/nsrt/bug-13358.php b/tests/PHPStan/Analyser/nsrt/bug-13358.php
index 43cdeeca2f..6482ddca2d 100644
--- a/tests/PHPStan/Analyser/nsrt/bug-13358.php
+++ b/tests/PHPStan/Analyser/nsrt/bug-13358.php
@@ -1,5 +1,5 @@
-<?php declare(strict_types = 1);
-
+<?php // lint >= 8.0
+declare(strict_types = 1);
 namespace Bug13358;
 
 use function PHPStan\Testing\assertType;
diff --git a/tests/PHPStan/Analyser/nsrt/bug-14319.php b/tests/PHPStan/Analyser/nsrt/bug-14319.php
index cbf89d13dc..c253aa5cdc 100644
--- a/tests/PHPStan/Analyser/nsrt/bug-14319.php
+++ b/tests/PHPStan/Analyser/nsrt/bug-14319.php
@@ -1,4 +1,4 @@
-<?php
+<?php // lint >= 8.0
 
 namespace Bug14319;
 
diff --git a/tests/PHPStan/Analyser/nsrt/bug-14710.php b/tests/PHPStan/Analyser/nsrt/bug-14710.php
index 6d208e77ca..711580f536 100644
--- a/tests/PHPStan/Analyser/nsrt/bug-14710.php
+++ b/tests/PHPStan/Analyser/nsrt/bug-14710.php
@@ -1,5 +1,5 @@
-<?php declare(strict_types = 1);
-
+<?php // lint >= 8.0
+declare(strict_types = 1);
 namespace Bug14710;
 
 use function PHPStan\Testing\assertType;
diff --git a/tests/PHPStan/Analyser/nsrt/bug-7259.php b/tests/PHPStan/Analyser/nsrt/bug-7259.php
index df6eb0aaf4..571e61f009 100644
--- a/tests/PHPStan/Analyser/nsrt/bug-7259.php
+++ b/tests/PHPStan/Analyser/nsrt/bug-7259.php
@@ -1,5 +1,5 @@
-<?php declare(strict_types = 1);
-
+<?php // lint >= 8.0
+declare(strict_types = 1);
 namespace Bug7259;
 
 use function PHPStan\Testing\assertType;
diff --git a/tests/PHPStan/Analyser/nsrt/bug-7987.php b/tests/PHPStan/Analyser/nsrt/bug-7987.php
index 23bda9fb31..ed7a2a8609 100644
--- a/tests/PHPStan/Analyser/nsrt/bug-7987.php
+++ b/tests/PHPStan/Analyser/nsrt/bug-7987.php
@@ -1,5 +1,5 @@
-<?php declare(strict_types=1);
-
+<?php // lint >= 8.0
+declare(strict_types=1);
 namespace Bug7987;
 
 use function PHPStan\Testing\assertType;
diff --git a/tests/PHPStan/Analyser/nsrt/bug-9208.php b/tests/PHPStan/Analyser/nsrt/bug-9208.php
index fa9ec21a30..923c7e7ba4 100644
--- a/tests/PHPStan/Analyser/nsrt/bug-9208.php
+++ b/tests/PHPStan/Analyser/nsrt/bug-9208.php
@@ -1,4 +1,4 @@
-<?php
+<?php // lint >= 8.0
 
 namespace Bug9208;
 
diff --git a/tests/PHPStan/Analyser/nsrt/bug-9360.php b/tests/PHPStan/Analyser/nsrt/bug-9360.php
index 668affdb43..1c1b667fab 100644
--- a/tests/PHPStan/Analyser/nsrt/bug-9360.php
+++ b/tests/PHPStan/Analyser/nsrt/bug-9360.php
@@ -1,5 +1,5 @@
-<?php declare(strict_types = 1);
-
+<?php // lint >= 8.0
+declare(strict_types = 1);
 namespace Bug9360;
 
 use function PHPStan\Testing\assertType;
diff --git a/tests/PHPStan/Analyser/nsrt/bug-9404.php b/tests/PHPStan/Analyser/nsrt/bug-9404.php
index e03c4cd386..232648aa8f 100644
--- a/tests/PHPStan/Analyser/nsrt/bug-9404.php
+++ b/tests/PHPStan/Analyser/nsrt/bug-9404.php
@@ -1,4 +1,4 @@
-<?php
+<?php // lint >= 8.0
 
 namespace Bug9404;
 
diff --git a/tests/PHPStan/Analyser/nsrt/date-format.php b/tests/PHPStan/Analyser/nsrt/date-format.php
index 2f11a33471..e01319f280 100644
--- a/tests/PHPStan/Analyser/nsrt/date-format.php
+++ b/tests/PHPStan/Analyser/nsrt/date-format.php
@@ -1,4 +1,4 @@
-<?php
+<?php // lint >= 8.0
 
 namespace DateFormatReturnType;
 
diff --git a/tests/PHPStan/Analyser/nsrt/native-expressions.php b/tests/PHPStan/Analyser/nsrt/native-expressions.php
index abe041686a..9af55763dd 100644
--- a/tests/PHPStan/Analyser/nsrt/native-expressions.php
+++ b/tests/PHPStan/Analyser/nsrt/native-expressions.php
@@ -1,4 +1,4 @@
-<?php
+<?php // lint >= 8.0
 
 namespace NativeExpressions;
 
diff --git a/tests/PHPStan/Analyser/nsrt/preg_split.php b/tests/PHPStan/Analyser/nsrt/preg_split.php
index 210a467372..5980f4ad12 100644
--- a/tests/PHPStan/Analyser/nsrt/preg_split.php
+++ b/tests/PHPStan/Analyser/nsrt/preg_split.php
@@ -1,4 +1,4 @@
-<?php
+<?php // lint >= 8.0
 
 namespace PregSplit;
 
diff --git a/tests/PHPStan/Build/RequiredPhpVersionCommentTest.php b/tests/PHPStan/Build/RequiredPhpVersionCommentTest.php
index 5af1af0dc0..9adde3a4c3 100644
--- a/tests/PHPStan/Build/RequiredPhpVersionCommentTest.php
+++ b/tests/PHPStan/Build/RequiredPhpVersionCommentTest.php
@@ -123,6 +123,9 @@ public static function dataDetectedVersion(): iterable
 		yield 'enum' => ['<?php enum Foo { case A; }', 80100];
 		yield 'readonly property' => ['<?php class Foo { public readonly int $x; }', 80100];
 		yield 'readonly promoted property' => ['<?php class Foo { public function __construct(public readonly int $x) {} }', 80100];
+		yield 'union type' => ['<?php function foo(A|B $x) {}', 80000];
+		yield 'union return type' => ['<?php function foo(): A|B {}', 80000];
+		yield 'nullable union type' => ['<?php function foo(A|null $x) {}', 80000];
 		yield 'intersection type' => ['<?php function foo(A&B $x) {}', 80100];
 		yield 'first-class callable' => ['<?php strlen(...);', 80100];
 		yield 'readonly class' => ['<?php readonly class Foo {}', 80200];
diff --git a/tests/PHPStan/Rules/Functions/data/bug-5760.php b/tests/PHPStan/Rules/Functions/data/bug-5760.php
index f3ec36535f..4b4260c66e 100644
--- a/tests/PHPStan/Rules/Functions/data/bug-5760.php
+++ b/tests/PHPStan/Rules/Functions/data/bug-5760.php
@@ -1,4 +1,4 @@
-<?php declare(strict_types=1);
+<?php declare(strict_types=1); // lint >= 8.0
 
 namespace Bug5760;
 
diff --git a/tests/PHPStan/Rules/Functions/data/bug-6448.php b/tests/PHPStan/Rules/Functions/data/bug-6448.php
index c2529c8713..d08399fcad 100644
--- a/tests/PHPStan/Rules/Functions/data/bug-6448.php
+++ b/tests/PHPStan/Rules/Functions/data/bug-6448.php
@@ -1,4 +1,4 @@
-<?php
+<?php // lint >= 8.0
 
 namespace Bug6448;
 
diff --git a/tests/PHPStan/Rules/Functions/data/bug-7138.php b/tests/PHPStan/Rules/Functions/data/bug-7138.php
index 28b6db70cf..ed10202d70 100644
--- a/tests/PHPStan/Rules/Functions/data/bug-7138.php
+++ b/tests/PHPStan/Rules/Functions/data/bug-7138.php
@@ -1,4 +1,4 @@
-<?php
+<?php // lint >= 8.0
 
 namespace Bug7138;
 
diff --git a/tests/PHPStan/Rules/Functions/data/bug-9652.php b/tests/PHPStan/Rules/Functions/data/bug-9652.php
index fa0c827443..2023c94144 100644
--- a/tests/PHPStan/Rules/Functions/data/bug-9652.php
+++ b/tests/PHPStan/Rules/Functions/data/bug-9652.php
@@ -1,4 +1,4 @@
-<?php declare(strict_types = 1);
+<?php declare(strict_types = 1); // lint >= 8.0
 
 namespace Bug9652;
 
diff --git a/tests/PHPStan/Rules/Methods/data/bug-11663.php b/tests/PHPStan/Rules/Methods/data/bug-11663.php
index ac2ed03a93..f21aa5f0cc 100644
--- a/tests/PHPStan/Rules/Methods/data/bug-11663.php
+++ b/tests/PHPStan/Rules/Methods/data/bug-11663.php
@@ -1,4 +1,4 @@
-<?php declare(strict_types = 1);
+<?php declare(strict_types = 1); // lint >= 8.0
 
 namespace Bug11663;
 
diff --git a/tests/PHPStan/Rules/Methods/data/bug-12558.php b/tests/PHPStan/Rules/Methods/data/bug-12558.php
index 88a8224924..c501c4137d 100644
--- a/tests/PHPStan/Rules/Methods/data/bug-12558.php
+++ b/tests/PHPStan/Rules/Methods/data/bug-12558.php
@@ -1,4 +1,4 @@
-<?php declare(strict_types = 1);
+<?php declare(strict_types = 1); // lint >= 8.0
 
 namespace Bug12558;
 
diff --git a/tests/PHPStan/Rules/Methods/data/bug-12884.php b/tests/PHPStan/Rules/Methods/data/bug-12884.php
index 20ec2cac5f..4955bd0f77 100644
--- a/tests/PHPStan/Rules/Methods/data/bug-12884.php
+++ b/tests/PHPStan/Rules/Methods/data/bug-12884.php
@@ -1,4 +1,4 @@
-<?php declare(strict_types = 1);
+<?php declare(strict_types = 1); // lint >= 8.0
 
 namespace Bug12884;
 
diff --git a/tests/PHPStan/Rules/Methods/data/bug-14617.php b/tests/PHPStan/Rules/Methods/data/bug-14617.php
index d8e81076d4..0ad5533fc0 100644
--- a/tests/PHPStan/Rules/Methods/data/bug-14617.php
+++ b/tests/PHPStan/Rules/Methods/data/bug-14617.php
@@ -1,4 +1,4 @@
-<?php declare(strict_types = 1);
+<?php declare(strict_types = 1); // lint >= 8.0
 
 namespace Bug14617;
 
diff --git a/tests/PHPStan/Rules/Methods/data/bug-8071.php b/tests/PHPStan/Rules/Methods/data/bug-8071.php
index 2acbb838ca..60793d5fa5 100644
--- a/tests/PHPStan/Rules/Methods/data/bug-8071.php
+++ b/tests/PHPStan/Rules/Methods/data/bug-8071.php
@@ -1,4 +1,4 @@
-<?php
+<?php // lint >= 8.0
 
 namespace Bug8071;
 
diff --git a/tests/PHPStan/Rules/Properties/data/invalid-callable-property-type.php b/tests/PHPStan/Rules/Properties/data/invalid-callable-property-type.php
index 053c0bfb1c..8deca5ff92 100644
--- a/tests/PHPStan/Rules/Properties/data/invalid-callable-property-type.php
+++ b/tests/PHPStan/Rules/Properties/data/invalid-callable-property-type.php
@@ -1,4 +1,4 @@
-<?php declare(strict_types = 1);
+<?php declare(strict_types = 1); // lint >= 8.0
 
 namespace InvalidCallablePropertyType;
 
diff --git a/tests/PHPStan/Rules/Types/data/invalid-union-with-never.php b/tests/PHPStan/Rules/Types/data/invalid-union-with-never.php
index d959067f89..00103eceaf 100644
--- a/tests/PHPStan/Rules/Types/data/invalid-union-with-never.php
+++ b/tests/PHPStan/Rules/Types/data/invalid-union-with-never.php
@@ -1,4 +1,4 @@
-<?php declare(strict_types=1);
+<?php declare(strict_types=1); // lint >= 8.0
 
 namespace InvalidUnionWithNever;
 
diff --git a/tests/PHPStan/Rules/Types/data/invalid-union-with-void.php b/tests/PHPStan/Rules/Types/data/invalid-union-with-void.php
index 8744da8a10..fee0b54ffa 100644
--- a/tests/PHPStan/Rules/Types/data/invalid-union-with-void.php
+++ b/tests/PHPStan/Rules/Types/data/invalid-union-with-void.php
@@ -1,4 +1,4 @@
-<?php declare(strict_types=1);
+<?php declare(strict_types=1); // lint >= 8.0
 
 namespace InvalidUnionWithVoid;