diff --git a/tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php b/tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php
index 0eea3694d1..c5fce4e73a 100644
--- a/tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php
+++ b/tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php
@@ -2053,4 +2053,35 @@ public function testBug7522(): void
 		$this->analyse([__DIR__ . '/data/bug-7522.php'], []);
 	}
 
+	public function testBug12847(): void
+	{
+		if (PHP_VERSION_ID < 80000) {
+			$this->markTestSkipped('Test requires PHP 8.0.');
+		}
+
+		$this->checkExplicitMixed = true;
+		$this->checkImplicitMixed = true;
+
+		$this->analyse([__DIR__ . '/data/bug-12847.php'], [
+			[
+				'Parameter #1 $array of function Bug12847\doSomething expects non-empty-array<mixed>, mixed given.',
+				32,
+				'mixed is empty.',
+			],
+			[
+				'Parameter #1 $array of function Bug12847\doSomething expects non-empty-array<mixed>, mixed given.',
+				39,
+				'mixed is empty.',
+			],
+			[
+				'Parameter #1 $array of function Bug12847\doSomethingWithInt expects non-empty-array<int>, non-empty-array given.',
+				61,
+			],
+			[
+				'Parameter #1 $array of function Bug12847\doSomethingWithInt expects non-empty-array<int>, non-empty-array given.',
+				67,
+			],
+		]);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Functions/data/bug-12847.php b/tests/PHPStan/Rules/Functions/data/bug-12847.php
new file mode 100644
index 0000000000..c4880d83f6
--- /dev/null
+++ b/tests/PHPStan/Rules/Functions/data/bug-12847.php
@@ -0,0 +1,69 @@
+<?php declare(strict_types = 1);
+
+namespace Bug12847;
+
+function doBar():void {
+	/**
+	 * @var array<mixed> $array
+	 */
+	$array = [
+		'abc' => 'def'
+	];
+
+	if (isset($array['def'])) {
+		doSomething($array);
+	}
+}
+
+function doFoo(array $array):void {
+	if (isset($array['def'])) {
+		doSomething($array);
+	}
+}
+
+function doFooBar(array $array):void {
+	if (array_key_exists('foo', $array) && $array['foo'] === 17) {
+		doSomething($array);
+	}
+}
+
+function doImplicitMixed($mixed):void {
+	if (isset($mixed['def'])) {
+		doSomething($mixed);
+	}
+}
+
+function doExplicitMixed(mixed $mixed): void
+{
+	if (isset($mixed['def'])) {
+		doSomething($mixed);
+	}
+}
+
+/**
+ * @param non-empty-array<mixed> $array
+ */
+function doSomething(array $array): void
+{
+
+}
+
+/**
+ * @param non-empty-array<int> $array
+ */
+function doSomethingWithInt(array $array): void
+{
+
+}
+
+function doFooBarInt(array $array):void {
+	if (array_key_exists('foo', $array) && $array['foo'] === 17) {
+		doSomethingWithInt($array); // expect error, because our array is not sealed
+	}
+}
+
+function doFooBarString(array $array):void {
+	if (array_key_exists('foo', $array) && $array['foo'] === "hello") {
+		doSomethingWithInt($array); // expect error, because our array is not sealed
+	}
+}