diff --git a/src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php b/src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php
index 30f7febe49..5ba1a88009 100644
--- a/src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php
+++ b/src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php
@@ -10,7 +10,6 @@
 use PHPStan\Rules\RuleErrorBuilder;
 use PHPStan\Rules\RuleLevelHelper;
 use PHPStan\Type\ErrorType;
-use PHPStan\Type\MixedType;
 use PHPStan\Type\Type;
 use PHPStan\Type\VerbosityLevel;
 use function sprintf;
@@ -41,19 +40,29 @@ public function processNode(Node $node, Scope $scope): array
 			return [];
 		}
 
-		$dimensionType = $scope->getType($node->dim);
-		if ($dimensionType instanceof MixedType) {
-			return [];
-		}
-
 		$varType = $this->ruleLevelHelper->findTypeToCheck(
 			$scope,
 			$node->var,
 			'',
-			static fn (Type $varType): bool => $varType->isArray()->no() || AllowedArrayKeysTypes::getType()->isSuperTypeOf($dimensionType)->yes(),
+			static fn (Type $varType): bool => $varType->isArray()->no(),
 		)->getType();
 
-		if ($varType instanceof ErrorType || $varType->isArray()->no()) {
+		if ($varType instanceof ErrorType) {
+			return [];
+		}
+
+		$isArray = $varType->isArray();
+		if ($isArray->no() || ($isArray->maybe() && !$this->reportMaybes)) {
+			return [];
+		}
+
+		$dimensionType = $this->ruleLevelHelper->findTypeToCheck(
+			$scope,
+			$node->dim,
+			'',
+			static fn (Type $dimType): bool => AllowedArrayKeysTypes::getType()->isSuperTypeOf($dimType)->yes(),
+		)->getType();
+		if ($dimensionType instanceof ErrorType) {
 			return [];
 		}
 
@@ -64,7 +73,11 @@ public function processNode(Node $node, Scope $scope): array
 
 		return [
 			RuleErrorBuilder::message(
-				sprintf('%s array key type %s.', $isSuperType->no() ? 'Invalid' : 'Possibly invalid', $dimensionType->describe(VerbosityLevel::typeOnly())),
+				sprintf(
+					'%s array key type %s.',
+					$isArray->yes() && $isSuperType->no() ? 'Invalid' : 'Possibly invalid',
+					$dimensionType->describe(VerbosityLevel::typeOnly()),
+				),
 			)->identifier('offsetAccess.invalidOffset')->build(),
 		];
 	}
diff --git a/src/Rules/RuleLevelHelper.php b/src/Rules/RuleLevelHelper.php
index 109b30a2b3..d82ff0745b 100644
--- a/src/Rules/RuleLevelHelper.php
+++ b/src/Rules/RuleLevelHelper.php
@@ -190,7 +190,11 @@ private function findTypeToCheckImplementation(
 		bool $isTopLevel = false,
 	): FoundTypeResult
 	{
-		if (!$this->checkNullables && !$type->isNull()->yes()) {
+		if (
+			!$this->checkNullables
+			&& !$type->isNull()->yes()
+			&& !$unionTypeCriteriaCallback(new NullType())
+		) {
 			$type = TypeCombinator::removeNull($type);
 		}
 
diff --git a/tests/PHPStan/Levels/LevelsIntegrationTest.php b/tests/PHPStan/Levels/LevelsIntegrationTest.php
index 12499dce44..044a088f60 100644
--- a/tests/PHPStan/Levels/LevelsIntegrationTest.php
+++ b/tests/PHPStan/Levels/LevelsIntegrationTest.php
@@ -41,6 +41,7 @@ public static function dataTopics(): array
 			['arrayDestructuring'],
 			['listType'],
 			['missingTypes'],
+			['arrayOffsetAccess'],
 		];
 		if (PHP_VERSION_ID >= 80300) {
 			$topics[] = ['constantAccesses83'];
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-10.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-10.json
new file mode 100644
index 0000000000..e0b5d1d2d8
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-10.json
@@ -0,0 +1,52 @@
+[
+    {
+        "message": "Possibly invalid array key type mixed.",
+        "line": 22,
+        "ignorable": true
+    },
+    {
+        "message": "Possibly invalid array key type mixed.",
+        "line": 31,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset 42 on mixed.",
+        "line": 42,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset null on mixed.",
+        "line": 43,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset DateTimeImmutable on mixed.",
+        "line": 44,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset int|null on mixed.",
+        "line": 45,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset int|object on mixed.",
+        "line": 46,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset object|null on mixed.",
+        "line": 47,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset mixed on mixed.",
+        "line": 48,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset mixed on mixed.",
+        "line": 49,
+        "ignorable": true
+    }
+]
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-3.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-3.json
new file mode 100644
index 0000000000..3e23caff09
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-3.json
@@ -0,0 +1,7 @@
+[
+    {
+        "message": "Invalid array key type DateTimeImmutable.",
+        "line": 17,
+        "ignorable": true
+    }
+]
\ No newline at end of file
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-4.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-4.json
new file mode 100644
index 0000000000..3f91016ab3
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-4.json
@@ -0,0 +1,142 @@
+[
+    {
+        "message": "Expression \"$a[42]\" on a separate line does not do anything.",
+        "line": 15,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$a[null]\" on a separate line does not do anything.",
+        "line": 16,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$a[$intOrNull]\" on a separate line does not do anything.",
+        "line": 18,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$a[$objectOrInt]\" on a separate line does not do anything.",
+        "line": 19,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$a[$objectOrNull]\" on a separate line does not do anything.",
+        "line": 20,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$a[$explicitlyMixed]\" on a separate line does not do anything.",
+        "line": 21,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$a[$implicitlyMixed]\" on a separate line does not do anything.",
+        "line": 22,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$arrayOrObject[42]\" on a separate line does not do anything.",
+        "line": 24,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$arrayOrObject[null]\" on a separate line does not do anything.",
+        "line": 25,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$arrayOrObject[$intOrNull]\" on a separate line does not do anything.",
+        "line": 27,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$arrayOrObject[$objectOrInt]\" on a separate line does not do anything.",
+        "line": 28,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$arrayOrObject[$objectOrNull]\" on a separate line does not do anything.",
+        "line": 29,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$arrayOrObject[$explicitlyMixed]\" on a separate line does not do anything.",
+        "line": 30,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$arrayOrObject[$implicitlyMixed]\" on a separate line does not do anything.",
+        "line": 31,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$explicitlyMixed[42]\" on a separate line does not do anything.",
+        "line": 33,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$explicitlyMixed[null]\" on a separate line does not do anything.",
+        "line": 34,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$explicitlyMixed[$intOrNull]\" on a separate line does not do anything.",
+        "line": 36,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$explicitlyMixed[$objectOrInt]\" on a separate line does not do anything.",
+        "line": 37,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$explicitlyMixed[$objectOrNull]\" on a separate line does not do anything.",
+        "line": 38,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$explicitlyMixed[$explicitlyMixed]\" on a separate line does not do anything.",
+        "line": 39,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$explicitlyMixed[$implicitlyMixed]\" on a separate line does not do anything.",
+        "line": 40,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$implicitlyMixed[42]\" on a separate line does not do anything.",
+        "line": 42,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$implicitlyMixed[null]\" on a separate line does not do anything.",
+        "line": 43,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$implicitlyMixed[$intOrNull]\" on a separate line does not do anything.",
+        "line": 45,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$implicitlyMixed[$objectOrInt]\" on a separate line does not do anything.",
+        "line": 46,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$implicitlyMixed[$objectOrNull]\" on a separate line does not do anything.",
+        "line": 47,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$implicitlyMixed[$explicitlyMixed]\" on a separate line does not do anything.",
+        "line": 48,
+        "ignorable": true
+    },
+    {
+        "message": "Expression \"$implicitlyMixed[$implicitlyMixed]\" on a separate line does not do anything.",
+        "line": 49,
+        "ignorable": true
+    }
+]
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json
new file mode 100644
index 0000000000..5c3bc3d299
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-6.json
@@ -0,0 +1,22 @@
+[
+    {
+        "message": "Method Levels\\ArrayOffsetAccess\\Foo::test() has parameter $a with no value type specified in iterable type array.",
+        "line": 13,
+        "ignorable": true
+    },
+    {
+      "message": "Method Levels\\ArrayOffsetAccess\\Foo::test() has parameter $arrayOrObject with generic interface ArrayAccess but does not specify its types: TKey, TValue",
+        "line": 13,
+        "ignorable": true
+    },
+    {
+      "message": "Method Levels\\ArrayOffsetAccess\\Foo::test() has parameter $arrayOrObject with no value type specified in iterable type array.",
+        "line": 13,
+        "ignorable": true
+    },
+    {
+        "message": "Method Levels\\ArrayOffsetAccess\\Foo::test() has parameter $implicitlyMixed with no type specified.",
+        "line": 13,
+        "ignorable": true
+    }
+]
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
new file mode 100644
index 0000000000..674057be06
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-7.json
@@ -0,0 +1,27 @@
+[
+    {
+        "message": "Possibly invalid array key type int|object.",
+        "line": 19,
+        "ignorable": true
+    },
+    {
+        "message": "Possibly invalid array key type object|null.",
+        "line": 20,
+        "ignorable": true
+    },
+    {
+        "message": "Possibly invalid array key type DateTimeImmutable.",
+        "line": 26,
+        "ignorable": true
+    },
+    {
+        "message": "Possibly invalid array key type int|object.",
+        "line": 28,
+        "ignorable": true
+    },
+    {
+        "message": "Possibly invalid array key type object|null.",
+        "line": 29,
+        "ignorable": true
+    }
+]
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess-9.json b/tests/PHPStan/Levels/data/arrayOffsetAccess-9.json
new file mode 100644
index 0000000000..edca311940
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess-9.json
@@ -0,0 +1,52 @@
+[
+    {
+        "message": "Possibly invalid array key type mixed.",
+        "line": 21,
+        "ignorable": true
+    },
+    {
+        "message": "Possibly invalid array key type mixed.",
+        "line": 30,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset 42 on mixed.",
+        "line": 33,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset null on mixed.",
+        "line": 34,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset DateTimeImmutable on mixed.",
+        "line": 35,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset int|null on mixed.",
+        "line": 36,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset int|object on mixed.",
+        "line": 37,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset object|null on mixed.",
+        "line": 38,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset mixed on mixed.",
+        "line": 39,
+        "ignorable": true
+    },
+    {
+        "message": "Cannot access offset mixed on mixed.",
+        "line": 40,
+        "ignorable": true
+    }
+]
diff --git a/tests/PHPStan/Levels/data/arrayOffsetAccess.php b/tests/PHPStan/Levels/data/arrayOffsetAccess.php
new file mode 100644
index 0000000000..362bb5c03f
--- /dev/null
+++ b/tests/PHPStan/Levels/data/arrayOffsetAccess.php
@@ -0,0 +1,51 @@
+<?php
+
+namespace Levels\ArrayOffsetAccess;
+
+class Foo {
+	/**
+	 * @param array|\ArrayAccess $arrayOrObject
+	 * @param int|null $intOrNull
+	 * @param object|int $objectOrInt
+	 * @param object|null $objectOrNull
+	 * @param mixed $explicitlyMixed
+	 */
+	public function test(array $a, $arrayOrObject, $intOrNull, $objectOrInt, $objectOrNull, $explicitlyMixed, $implicitlyMixed): void
+	{
+		$a[42];
+		$a[null];
+		$a[new \DateTimeImmutable()];
+		$a[$intOrNull];
+		$a[$objectOrInt];
+		$a[$objectOrNull];
+		$a[$explicitlyMixed];
+		$a[$implicitlyMixed];
+
+		$arrayOrObject[42];
+		$arrayOrObject[null];
+		$arrayOrObject[new \DateTimeImmutable()];
+		$arrayOrObject[$intOrNull];
+		$arrayOrObject[$objectOrInt];
+		$arrayOrObject[$objectOrNull];
+		$arrayOrObject[$explicitlyMixed];
+		$arrayOrObject[$implicitlyMixed];
+
+		$explicitlyMixed[42];
+		$explicitlyMixed[null];
+		$explicitlyMixed[new \DateTimeImmutable()];
+		$explicitlyMixed[$intOrNull];
+		$explicitlyMixed[$objectOrInt];
+		$explicitlyMixed[$objectOrNull];
+		$explicitlyMixed[$explicitlyMixed];
+		$explicitlyMixed[$implicitlyMixed];
+
+		$implicitlyMixed[42];
+		$implicitlyMixed[null];
+		$implicitlyMixed[new \DateTimeImmutable()];
+		$implicitlyMixed[$intOrNull];
+		$implicitlyMixed[$objectOrInt];
+		$implicitlyMixed[$objectOrNull];
+		$implicitlyMixed[$explicitlyMixed];
+		$implicitlyMixed[$implicitlyMixed];
+	}
+}