diff --git a/src/Rules/Pure/FunctionPurityCheck.php b/src/Rules/Pure/FunctionPurityCheck.php
index ccc85a1c24..a799cd4351 100644
--- a/src/Rules/Pure/FunctionPurityCheck.php
+++ b/src/Rules/Pure/FunctionPurityCheck.php
@@ -92,6 +92,11 @@ public function check(
 				count($throwPoints) === 0
 				&& count($impurePoints) === 0
 				&& count($functionReflection->getAsserts()->getAll()) === 0
+				&& (
+					!$functionReflection instanceof ExtendedMethodReflection
+					|| $functionReflection->isFinal()->yes()
+					|| $functionReflection->getDeclaringClass()->isFinal()
+				)
 			) {
 				$errors[] = RuleErrorBuilder::message(sprintf(
 					'%s is marked as impure but does not have any side effects.',
diff --git a/tests/PHPStan/Rules/Pure/PureMethodRuleTest.php b/tests/PHPStan/Rules/Pure/PureMethodRuleTest.php
index a483c6d580..c31874629d 100644
--- a/tests/PHPStan/Rules/Pure/PureMethodRuleTest.php
+++ b/tests/PHPStan/Rules/Pure/PureMethodRuleTest.php
@@ -220,4 +220,27 @@ public function testBug12224(): void
 		]);
 	}
 
+	public function testBug12382(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+		$this->analyse([__DIR__ . '/data/bug-12382.php'], [
+			[
+				'Method Bug12382\FinalHelloWorld1::dummy() is marked as impure but does not have any side effects.',
+				25,
+			],
+			[
+				'Method Bug12382\FinalHelloWorld2::dummy() is marked as impure but does not have any side effects.',
+				33,
+			],
+			[
+				'Method Bug12382\FinalHelloWorld3::dummy() is marked as impure but does not have any side effects.',
+				42,
+			],
+			[
+				'Method Bug12382\FinalHelloWorld4::dummy() is marked as impure but does not have any side effects.',
+				53,
+			],
+		]);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Pure/data/bug-12382.php b/tests/PHPStan/Rules/Pure/data/bug-12382.php
new file mode 100644
index 0000000000..7a66941da8
--- /dev/null
+++ b/tests/PHPStan/Rules/Pure/data/bug-12382.php
@@ -0,0 +1,56 @@
+<?php declare(strict_types = 1);
+
+namespace Bug12382;
+
+class HelloWorld
+{
+	/** @phpstan-impure */
+	public function dummy() : self{
+		return $this;
+	}
+}
+
+class Child extends HelloWorld{
+	private int $prop = 1;
+
+	public function dummy() : HelloWorld{
+		$this->prop++;
+		return $this;
+	}
+}
+
+final class FinalHelloWorld1
+{
+	/** @phpstan-impure */
+	public function dummy() : self{
+		return $this;
+	}
+}
+
+class FinalHelloWorld2
+{
+	/** @phpstan-impure */
+	final public function dummy() : self{
+		return $this;
+	}
+}
+
+/** @final */
+class FinalHelloWorld3
+{
+	/** @phpstan-impure */
+	public function dummy() : self{
+		return $this;
+	}
+}
+
+class FinalHelloWorld4
+{
+	/**
+	 * @final
+	 * @phpstan-impure
+	 */
+	public function dummy() : self{
+		return $this;
+	}
+}
diff --git a/tests/PHPStan/Rules/Pure/data/pure-constructor.php b/tests/PHPStan/Rules/Pure/data/pure-constructor.php
index 71045fd3ed..baa1f755cf 100644
--- a/tests/PHPStan/Rules/Pure/data/pure-constructor.php
+++ b/tests/PHPStan/Rules/Pure/data/pure-constructor.php
@@ -2,7 +2,7 @@
 
 namespace PureConstructor;
 
-class Foo
+final class Foo
 {
 
 	private string $prop;
@@ -21,7 +21,7 @@ public function __construct(
 
 }
 
-class Bar
+final class Bar
 {
 
 	private string $prop;
@@ -37,7 +37,7 @@ public function __construct(
 
 }
 
-class AssignOtherThanThis
+final class AssignOtherThanThis
 {
 	private int $i = 0;
 
diff --git a/tests/PHPStan/Rules/Pure/data/pure-method.php b/tests/PHPStan/Rules/Pure/data/pure-method.php
index efa83c9191..ba2ce7e3be 100644
--- a/tests/PHPStan/Rules/Pure/data/pure-method.php
+++ b/tests/PHPStan/Rules/Pure/data/pure-method.php
@@ -2,7 +2,7 @@
 
 namespace PureMethod;
 
-class Foo
+final class Foo
 {
 
 	/**
@@ -92,7 +92,7 @@ public function doFoo5()
 
 }
 
-class PureConstructor
+final class PureConstructor
 {
 
 	/**
@@ -105,7 +105,7 @@ public function __construct()
 
 }
 
-class ImpureConstructor
+final class ImpureConstructor
 {
 
 	/**
@@ -118,7 +118,7 @@ public function __construct()
 
 }
 
-class PossiblyImpureConstructor
+final class PossiblyImpureConstructor
 {
 
 	public function __construct()
@@ -128,7 +128,7 @@ public function __construct()
 
 }
 
-class TestConstructors
+final class TestConstructors
 {
 
 	/**
@@ -144,7 +144,7 @@ public function doFoo(string $s)
 
 }
 
-class ActuallyPure
+final class ActuallyPure
 {
 
 	/**
@@ -175,7 +175,7 @@ public function impure(): int
 
 }
 
-class ExtendingClass extends ToBeExtended
+final class ExtendingClass extends ToBeExtended
 {
 
 	public function pure(): int
@@ -191,7 +191,7 @@ public function impure(): int
 
 }
 
-class ClassWithVoidMethods
+final class ClassWithVoidMethods
 {
 
 	public function voidFunctionThatThrows(): void
@@ -235,12 +235,12 @@ public function purePostGetAssign(array $post = [], array $get = []): int
 
 }
 
-class NoMagicMethods
+final class NoMagicMethods
 {
 
 }
 
-class PureMagicMethods
+final class PureMagicMethods
 {
 
 	/**
@@ -253,7 +253,7 @@ public function __toString(): string
 
 }
 
-class MaybePureMagicMethods
+final class MaybePureMagicMethods
 {
 
 	public function __toString(): string
@@ -263,7 +263,7 @@ public function __toString(): string
 
 }
 
-class ImpureMagicMethods
+final class ImpureMagicMethods
 {
 
 	/**
@@ -277,7 +277,7 @@ public function __toString(): string
 
 }
 
-class TestMagicMethods
+final class TestMagicMethods
 {
 
 	/**
@@ -298,12 +298,12 @@ public function doFoo(
 
 }
 
-class NoConstructor
+final class NoConstructor
 {
 
 }
 
-class TestNoConstructor
+final class TestNoConstructor
 {
 
 	/**
@@ -318,7 +318,7 @@ public function doFoo(): int
 
 }
 
-class MaybeCallableFromUnion
+final class MaybeCallableFromUnion
 {
 
 	/**
@@ -334,7 +334,7 @@ public function doFoo($p): int
 
 }
 
-class VoidMethods
+final class VoidMethods
 {
 
 	private function doFoo(): void
@@ -361,7 +361,7 @@ private function doBaz(): void
 
 }
 
-class AssertingImpureVoidMethod
+final class AssertingImpureVoidMethod
 {
 
 	/**
@@ -376,7 +376,7 @@ public function assertSth($value): void
 
 }
 
-class StaticMethodAccessingStaticProperty
+final class StaticMethodAccessingStaticProperty
 {
 	/** @var int */
 	public static $a = 0;
@@ -397,7 +397,7 @@ public static function getB(): int
 	}
 }
 
-class StaticMethodAssigningStaticProperty
+final class StaticMethodAssigningStaticProperty
 {
 	/** @var int */
 	public static $a = 0;