diff --git a/build/PHPStan/Build/FinalClassRule.php b/build/PHPStan/Build/FinalClassRule.php
new file mode 100644
index 0000000000..c094aadda6
--- /dev/null
+++ b/build/PHPStan/Build/FinalClassRule.php
@@ -0,0 +1,64 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Build;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\Node\InClassNode;
+use PHPStan\Reflection\FunctionVariant;
+use PHPStan\Reflection\FunctionVariantWithPhpDocs;
+use PHPStan\Reflection\Php\DummyParameter;
+use PHPStan\Reflection\Php\PhpFunctionFromParserNodeReflection;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+use PHPStan\Type\Type;
+use function in_array;
+use function sprintf;
+
+/**
+ * @implements Rule<InClassNode>
+ */
+final class FinalClassRule implements Rule
+{
+
+	public function getNodeType(): string
+	{
+		return InClassNode::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		$classReflection = $node->getClassReflection();
+		if (!$classReflection->isClass()) {
+			return [];
+		}
+		if ($classReflection->isAbstract()) {
+			return [];
+		}
+		if ($classReflection->isFinal()) {
+			return [];
+		}
+		if ($classReflection->isSubclassOf(Type::class)) {
+			return [];
+		}
+
+		// exceptions
+		if (in_array($classReflection->getName(), [
+			FunctionVariant::class,
+			FunctionVariantWithPhpDocs::class,
+			DummyParameter::class,
+			PhpFunctionFromParserNodeReflection::class,
+		], true)) {
+			return [];
+		}
+
+		return [
+			RuleErrorBuilder::message(
+				sprintf('Class %s must be abstract or final.', $classReflection->getDisplayName()),
+			)
+				->identifier('phpstan.finalClass')
+				->build(),
+		];
+	}
+
+}
diff --git a/build/phpstan.neon b/build/phpstan.neon
index 63e9a82ace..bfb9493112 100644
--- a/build/phpstan.neon
+++ b/build/phpstan.neon
@@ -9,6 +9,7 @@ includes:
 	- ../phpstan-baseline.php
 	- ignore-by-php-version.neon.php
 	- ignore-by-architecture.neon.php
+
 parameters:
 	level: 8
 	paths:
@@ -98,6 +99,9 @@ parameters:
 		- stubs/NetteDIContainer.stub
 		- stubs/PhpParserName.stub
 
+rules:
+	- PHPStan\Build\FinalClassRule
+
 services:
 	-
 		class: PHPStan\Build\ServiceLocatorDynamicReturnTypeExtension