diff --git a/src/Rules/Properties/ReadOnlyByPhpDocPropertyAssignRule.php b/src/Rules/Properties/ReadOnlyByPhpDocPropertyAssignRule.php
index 70f18bcbcc..4c475096ef 100644
--- a/src/Rules/Properties/ReadOnlyByPhpDocPropertyAssignRule.php
+++ b/src/Rules/Properties/ReadOnlyByPhpDocPropertyAssignRule.php
@@ -2,8 +2,11 @@
 
 namespace PHPStan\Rules\Properties;
 
+use ArrayAccess;
 use PhpParser\Node;
 use PHPStan\Analyser\Scope;
+use PHPStan\Node\Expr\SetOffsetValueTypeExpr;
+use PHPStan\Node\Expr\UnsetOffsetExpr;
 use PHPStan\Node\PropertyAssignNode;
 use PHPStan\Reflection\ConstructorsHelper;
 use PHPStan\Reflection\MethodReflection;
@@ -11,6 +14,7 @@
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
 use PHPStan\ShouldNotHappenException;
+use PHPStan\Type\ObjectType;
 use PHPStan\Type\TypeUtils;
 use function in_array;
 use function sprintf;
@@ -106,6 +110,14 @@ public function processNode(Node $node, Scope $scope): array
 				continue;
 			}
 
+			$assignedExpr = $node->getAssignedExpr();
+			if (
+				($assignedExpr instanceof SetOffsetValueTypeExpr || $assignedExpr instanceof UnsetOffsetExpr)
+				&& (new ObjectType(ArrayAccess::class))->isSuperTypeOf($scope->getType($assignedExpr->getVar()))->yes()
+			) {
+				continue;
+			}
+
 			$errors[] = RuleErrorBuilder::message(sprintf('@readonly property %s::$%s is assigned outside of the constructor.', $declaringClass->getDisplayName(), $propertyReflection->getName()))
 				->identifier('property.readOnlyByPhpDocAssignNotInConstructor')
 				->build();
diff --git a/src/Rules/Properties/ReadOnlyPropertyAssignRule.php b/src/Rules/Properties/ReadOnlyPropertyAssignRule.php
index 4e9673070f..eac07303a2 100644
--- a/src/Rules/Properties/ReadOnlyPropertyAssignRule.php
+++ b/src/Rules/Properties/ReadOnlyPropertyAssignRule.php
@@ -2,14 +2,18 @@
 
 namespace PHPStan\Rules\Properties;
 
+use ArrayAccess;
 use PhpParser\Node;
 use PHPStan\Analyser\Scope;
+use PHPStan\Node\Expr\SetOffsetValueTypeExpr;
+use PHPStan\Node\Expr\UnsetOffsetExpr;
 use PHPStan\Node\PropertyAssignNode;
 use PHPStan\Reflection\ConstructorsHelper;
 use PHPStan\Reflection\MethodReflection;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
 use PHPStan\ShouldNotHappenException;
+use PHPStan\Type\ObjectType;
 use PHPStan\Type\TypeUtils;
 use function in_array;
 use function sprintf;
@@ -89,6 +93,14 @@ public function processNode(Node $node, Scope $scope): array
 				continue;
 			}
 
+			$assignedExpr = $node->getAssignedExpr();
+			if (
+				($assignedExpr instanceof SetOffsetValueTypeExpr || $assignedExpr instanceof UnsetOffsetExpr)
+				&& (new ObjectType(ArrayAccess::class))->isSuperTypeOf($scope->getType($assignedExpr->getVar()))->yes()
+			) {
+				continue;
+			}
+
 			$errors[] = RuleErrorBuilder::message(sprintf('Readonly property %s::$%s is assigned outside of the constructor.', $declaringClass->getDisplayName(), $propertyReflection->getName()))
 				->identifier('property.readOnlyAssignNotInConstructor')
 				->build();
diff --git a/tests/PHPStan/Rules/Properties/ReadOnlyByPhpDocPropertyAssignRuleTest.php b/tests/PHPStan/Rules/Properties/ReadOnlyByPhpDocPropertyAssignRuleTest.php
index c7ec6ed0ad..0aecf4c09c 100644
--- a/tests/PHPStan/Rules/Properties/ReadOnlyByPhpDocPropertyAssignRuleTest.php
+++ b/tests/PHPStan/Rules/Properties/ReadOnlyByPhpDocPropertyAssignRuleTest.php
@@ -125,6 +125,10 @@ public function testRule(): void
 				'@readonly property ReadonlyPropertyAssignPhpDoc\C::$c is assigned outside of the constructor.',
 				293,
 			],
+			[
+				'@readonly property ReadonlyPropertyAssignPhpDoc\ArrayAccessPropertyFetch::$storage is assigned outside of the constructor.',
+				311,
+			],
 		]);
 	}
 
diff --git a/tests/PHPStan/Rules/Properties/ReadOnlyPropertyAssignRuleTest.php b/tests/PHPStan/Rules/Properties/ReadOnlyPropertyAssignRuleTest.php
index 966f8e9e41..d54ae3a02f 100644
--- a/tests/PHPStan/Rules/Properties/ReadOnlyPropertyAssignRuleTest.php
+++ b/tests/PHPStan/Rules/Properties/ReadOnlyPropertyAssignRuleTest.php
@@ -123,6 +123,11 @@ public function testRule(): void
 			];
 		}
 
+		$errors[] = [
+			'Readonly property ReadonlyPropertyAssign\ArrayAccessPropertyFetch::$storage is assigned outside of the constructor.',
+			212,
+		];
+
 		$this->analyse([__DIR__ . '/data/readonly-assign.php'], $errors);
 	}
 
@@ -168,4 +173,22 @@ public function testBug6773(): void
 		]);
 	}
 
+	public function testBug8929(): void
+	{
+		if (PHP_VERSION_ID < 80100) {
+			$this->markTestSkipped('Test requires PHP 8.1.');
+		}
+
+		$this->analyse([__DIR__ . '/data/bug-8929.php'], []);
+	}
+
+	public function testBug12537(): void
+	{
+		if (PHP_VERSION_ID < 80100) {
+			$this->markTestSkipped('Test requires PHP 8.1.');
+		}
+
+		$this->analyse([__DIR__ . '/data/bug-12537.php'], []);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Properties/data/bug-12537.php b/tests/PHPStan/Rules/Properties/data/bug-12537.php
new file mode 100755
index 0000000000..85ae54496e
--- /dev/null
+++ b/tests/PHPStan/Rules/Properties/data/bug-12537.php
@@ -0,0 +1,31 @@
+<?php declare(strict_types = 1); // lint >= 8.1
+
+namespace Bug12537;
+
+use WeakMap;
+
+class Metadata {
+	/**
+	 * @var WeakMap<stdClass, int>
+	 */
+	private readonly WeakMap $storage;
+
+	public function __construct() {
+		$this->storage = new WeakMap();
+	}
+
+	public function set(stdClass $class, int $value): void {
+		$this->storage[$class] = $value;
+	}
+
+	public function get(stdClass $class): mixed {
+		return $this->storage[$class] ?? null;
+	}
+}
+
+$class = new stdClass();
+$meta  = new Metadata();
+
+$meta->set($class, 123);
+
+var_dump($meta->get($class));
diff --git a/tests/PHPStan/Rules/Properties/data/bug-8929.php b/tests/PHPStan/Rules/Properties/data/bug-8929.php
new file mode 100755
index 0000000000..4138ce73c9
--- /dev/null
+++ b/tests/PHPStan/Rules/Properties/data/bug-8929.php
@@ -0,0 +1,19 @@
+<?php declare(strict_types = 1); // lint >= 8.1
+
+namespace Bug8929;
+
+class Test
+{
+	/** @var \WeakMap<object, mixed> */
+	protected readonly \WeakMap $cache;
+
+	public function __construct()
+	{
+		$this->cache = new \WeakMap();
+	}
+
+	public function add(object $key, mixed $value): void
+	{
+		$this->cache[$key] = $value;
+	}
+}
diff --git a/tests/PHPStan/Rules/Properties/data/readonly-assign-phpdoc.php b/tests/PHPStan/Rules/Properties/data/readonly-assign-phpdoc.php
index 55af82fe30..c390bbb6da 100644
--- a/tests/PHPStan/Rules/Properties/data/readonly-assign-phpdoc.php
+++ b/tests/PHPStan/Rules/Properties/data/readonly-assign-phpdoc.php
@@ -294,3 +294,21 @@ public function mod()
 	}
 
 }
+
+class ArrayAccessPropertyFetch
+{
+
+	/** @readonly */
+	private \ArrayObject $storage;
+
+	public function __construct() {
+		$this->storage = new \ArrayObject();
+	}
+
+	public function set(\stdClass $class, int $value): void {
+		$this->storage[$class] = $value;
+		unset($this->storage[$class]);
+		$this->storage = new \WeakMap(); // invalid
+	}
+
+}
diff --git a/tests/PHPStan/Rules/Properties/data/readonly-assign.php b/tests/PHPStan/Rules/Properties/data/readonly-assign.php
index fe4af36466..e23655217c 100644
--- a/tests/PHPStan/Rules/Properties/data/readonly-assign.php
+++ b/tests/PHPStan/Rules/Properties/data/readonly-assign.php
@@ -196,3 +196,20 @@ protected function setUp(): void
 	}
 
 }
+
+class ArrayAccessPropertyFetch
+{
+
+	private readonly \ArrayObject $storage;
+
+	public function __construct() {
+		$this->storage = new \ArrayObject();
+	}
+
+	public function set(\stdClass $class, int $value): void {
+		$this->storage[$class] = $value;
+		unset($this->storage[$class]);
+		$this->storage = new \WeakMap(); // invalid
+	}
+
+}