diff --git a/src/Reflection/Mixin/MixinMethodsClassReflectionExtension.php b/src/Reflection/Mixin/MixinMethodsClassReflectionExtension.php
index 508074e4be..e2dac5a160 100644
--- a/src/Reflection/Mixin/MixinMethodsClassReflectionExtension.php
+++ b/src/Reflection/Mixin/MixinMethodsClassReflectionExtension.php
@@ -8,6 +8,7 @@
 use PHPStan\Reflection\MethodsClassReflectionExtension;
 use PHPStan\ShouldNotHappenException;
 use PHPStan\Type\TypeUtils;
+use PHPStan\Type\VerbosityLevel;
 use function array_intersect;
 use function count;
 
@@ -17,6 +18,9 @@ class MixinMethodsClassReflectionExtension implements MethodsClassReflectionExte
 	/** @var string[] */
 	private array $mixinExcludeClasses;
 
+	/** @var array<string, array<string, true>> */
+	private array $inProcess = [];
+
 	/**
 	 * @param string[] $mixinExcludeClasses
 	 */
@@ -48,11 +52,22 @@ private function findMethod(ClassReflection $classReflection, string $methodName
 				continue;
 			}
 
+			$typeDescription = $type->describe(VerbosityLevel::typeOnly());
+			if (isset($this->inProcess[$typeDescription][$methodName])) {
+				continue;
+			}
+
+			$this->inProcess[$typeDescription][$methodName] = true;
+
 			if (!$type->hasMethod($methodName)->yes()) {
+				unset($this->inProcess[$typeDescription][$methodName]);
 				continue;
 			}
 
 			$method = $type->getMethod($methodName, new OutOfClassScope());
+
+			unset($this->inProcess[$typeDescription][$methodName]);
+
 			$static = $method->isStatic();
 			if (
 				!$static
diff --git a/src/Reflection/Mixin/MixinPropertiesClassReflectionExtension.php b/src/Reflection/Mixin/MixinPropertiesClassReflectionExtension.php
index 3f0c947184..86b9242745 100644
--- a/src/Reflection/Mixin/MixinPropertiesClassReflectionExtension.php
+++ b/src/Reflection/Mixin/MixinPropertiesClassReflectionExtension.php
@@ -8,6 +8,7 @@
 use PHPStan\Reflection\PropertyReflection;
 use PHPStan\ShouldNotHappenException;
 use PHPStan\Type\TypeUtils;
+use PHPStan\Type\VerbosityLevel;
 use function array_intersect;
 use function count;
 
@@ -17,6 +18,9 @@ class MixinPropertiesClassReflectionExtension implements PropertiesClassReflecti
 	/** @var string[] */
 	private array $mixinExcludeClasses;
 
+	/** @var array<string, array<string, true>> */
+	private array $inProcess = [];
+
 	/**
 	 * @param string[] $mixinExcludeClasses
 	 */
@@ -48,11 +52,22 @@ private function findProperty(ClassReflection $classReflection, string $property
 				continue;
 			}
 
+			$typeDescription = $type->describe(VerbosityLevel::typeOnly());
+			if (isset($this->inProcess[$typeDescription][$propertyName])) {
+				continue;
+			}
+
+			$this->inProcess[$typeDescription][$propertyName] = true;
+
 			if (!$type->hasProperty($propertyName)->yes()) {
+				unset($this->inProcess[$typeDescription][$propertyName]);
 				continue;
 			}
 
-			return $type->getProperty($propertyName, new OutOfClassScope());
+			$property = $type->getProperty($propertyName, new OutOfClassScope());
+			unset($this->inProcess[$typeDescription][$propertyName]);
+
+			return $property;
 		}
 
 		foreach ($classReflection->getParents() as $parentClass) {
diff --git a/tests/PHPStan/Analyser/AnalyserIntegrationTest.php b/tests/PHPStan/Analyser/AnalyserIntegrationTest.php
index 5b28bbfe5b..9d11389b7e 100644
--- a/tests/PHPStan/Analyser/AnalyserIntegrationTest.php
+++ b/tests/PHPStan/Analyser/AnalyserIntegrationTest.php
@@ -489,6 +489,17 @@ public function testBug6255(): void
 		$this->assertNoErrors($errors);
 	}
 
+	public function testBug6300(): void
+	{
+		$errors = $this->runAnalyse(__DIR__ . '/data/bug-6300.php');
+		$this->assertCount(2, $errors);
+		$this->assertSame('Call to an undefined method Bug6300\Bar::get().', $errors[0]->getMessage());
+		$this->assertSame(23, $errors[0]->getLine());
+
+		$this->assertSame('Access to an undefined property Bug6300\Bar::$fooProp.', $errors[1]->getMessage());
+		$this->assertSame(24, $errors[1]->getLine());
+	}
+
 	/**
 	 * @return Error[]
 	 */
diff --git a/tests/PHPStan/Analyser/data/bug-6300.php b/tests/PHPStan/Analyser/data/bug-6300.php
new file mode 100644
index 0000000000..c9244c6cec
--- /dev/null
+++ b/tests/PHPStan/Analyser/data/bug-6300.php
@@ -0,0 +1,26 @@
+<?php
+
+namespace Bug6300;
+
+/**
+ * @mixin Bar
+ */
+class Foo
+{
+
+}
+
+/**
+ * @mixin Foo
+ */
+class Bar
+{
+
+}
+
+function (Bar $b): void
+{
+	$b->get();
+	echo $b->fooProp;
+};
+