diff --git a/.github/workflows/continuous-integration.yml b/.github/workflows/continuous-integration.yml
index 2ad7f282..0c4ea23b 100644
--- a/.github/workflows/continuous-integration.yml
+++ b/.github/workflows/continuous-integration.yml
@@ -22,7 +22,7 @@ jobs:
         deps:
           - "highest"
         include:
-          - deps: "low"
+          - deps: "lowest"
             php-version: "7.2"
 
     steps:
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 00000000..268200ad
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,11 @@
+# Circular dependency
+
+This package has a development dependency on `doctrine/common`, which has a
+regular dependency on this package (`^2.0` at the time of writing).
+
+To be able to use Composer, one has to let it understand that this is version 2
+(even when developing on 3.0.x), as follows:
+
+```shell
+COMPOSER_ROOT_VERSION=2.0 composer update -v
+```
diff --git a/lib/Doctrine/Persistence/Event/LoadClassMetadataEventArgs.php b/lib/Doctrine/Persistence/Event/LoadClassMetadataEventArgs.php
index b313f541..6a71fd11 100644
--- a/lib/Doctrine/Persistence/Event/LoadClassMetadataEventArgs.php
+++ b/lib/Doctrine/Persistence/Event/LoadClassMetadataEventArgs.php
@@ -13,7 +13,10 @@
  */
 class LoadClassMetadataEventArgs extends EventArgs
 {
-    /** @psalm-var ClassMetadata<object> */
+    /**
+     * @var ClassMetadata
+     * @psalm-var ClassMetadata<object>
+     */
     private $classMetadata;
 
     /** @var ObjectManager */
@@ -31,6 +34,7 @@ public function __construct(ClassMetadata $classMetadata, ObjectManager $objectM
     /**
      * Retrieves the associated ClassMetadata.
      *
+     * @return ClassMetadata
      * @psalm-return ClassMetadata<object>
      */
     public function getClassMetadata()
diff --git a/lib/Doctrine/Persistence/Mapping/Driver/AnnotationDriver.php b/lib/Doctrine/Persistence/Mapping/Driver/AnnotationDriver.php
index b607e379..a067606f 100644
--- a/lib/Doctrine/Persistence/Mapping/Driver/AnnotationDriver.php
+++ b/lib/Doctrine/Persistence/Mapping/Driver/AnnotationDriver.php
@@ -21,7 +21,6 @@
 use function in_array;
 use function is_array;
 use function is_dir;
-use function is_string;
 use function preg_match;
 use function preg_quote;
 use function realpath;
@@ -235,10 +234,9 @@ public function getAllClassNames()
                 }
 
                 foreach ($this->excludePaths as $excludePath) {
-                    $realpath = realpath($excludePath);
-                    assert(is_string($realpath));
-
-                    $exclude = str_replace('\\', '/', $realpath);
+                    $realExcludePath = realpath($excludePath);
+                    assert($realExcludePath !== false);
+                    $exclude = str_replace('\\', '/', $realExcludePath);
                     $current = str_replace('\\', '/', $sourceFile);
 
                     if (strpos($current, $exclude) !== false) {
diff --git a/lib/Doctrine/Persistence/Mapping/Driver/FileDriver.php b/lib/Doctrine/Persistence/Mapping/Driver/FileDriver.php
index 5fd4e709..0b9ae8a6 100644
--- a/lib/Doctrine/Persistence/Mapping/Driver/FileDriver.php
+++ b/lib/Doctrine/Persistence/Mapping/Driver/FileDriver.php
@@ -26,7 +26,10 @@ abstract class FileDriver implements MappingDriver
     /** @var FileLocator */
     protected $locator;
 
-    /** @psalm-var ClassMetadata<object>[]|null */
+    /**
+     * @var ClassMetadata[]|null
+     * @psalm-var ClassMetadata<object>[]|null
+     */
     protected $classCache;
 
     /** @var string */
@@ -72,7 +75,8 @@ public function getGlobalBasename()
      * Gets the element of schema meta data for the class from the mapping file.
      * This will lazily load the mapping file if it is not loaded yet.
      *
-     * @psalm-return ClassMetadata<object> The element of schema meta data.
+     * @return ClassMetadata The element of schema meta data.
+     * @psalm-return ClassMetadata<object>
      *
      * @throws MappingException
      */
diff --git a/lib/Doctrine/Persistence/Mapping/Driver/MappingDriver.php b/lib/Doctrine/Persistence/Mapping/Driver/MappingDriver.php
index 423824e4..0a635d6b 100644
--- a/lib/Doctrine/Persistence/Mapping/Driver/MappingDriver.php
+++ b/lib/Doctrine/Persistence/Mapping/Driver/MappingDriver.php
@@ -14,7 +14,7 @@ interface MappingDriver
     /**
      * Loads the metadata for the specified class into the provided container.
      *
-     * @param ClassMetadata<object> $metadata
+     * @psalm-param ClassMetadata<object> $metadata
      *
      * @return void
      */
diff --git a/lib/Doctrine/Persistence/Mapping/Driver/PHPDriver.php b/lib/Doctrine/Persistence/Mapping/Driver/PHPDriver.php
index dbbbfc27..cd74e9ff 100644
--- a/lib/Doctrine/Persistence/Mapping/Driver/PHPDriver.php
+++ b/lib/Doctrine/Persistence/Mapping/Driver/PHPDriver.php
@@ -12,7 +12,10 @@
  */
 class PHPDriver extends FileDriver
 {
-    /** @var ClassMetadata<object> */
+    /**
+     * @var ClassMetadata
+     * @psalm-var ClassMetadata<object>
+     */
     protected $metadata;
 
     /**
diff --git a/lib/Doctrine/Persistence/Mapping/ReflectionService.php b/lib/Doctrine/Persistence/Mapping/ReflectionService.php
index d955a0e7..9484e1f3 100644
--- a/lib/Doctrine/Persistence/Mapping/ReflectionService.php
+++ b/lib/Doctrine/Persistence/Mapping/ReflectionService.php
@@ -48,7 +48,8 @@ public function getClassNamespace(string $class);
      *
      * @psalm-param class-string<T> $class
      *
-     * @return ReflectionClass<T>|null
+     * @return ReflectionClass|null
+     * @psalm-return ReflectionClass<T>|null
      *
      * @template T of object
      */
diff --git a/lib/Doctrine/Persistence/Mapping/RuntimeReflectionService.php b/lib/Doctrine/Persistence/Mapping/RuntimeReflectionService.php
index 17bc743a..4ad42e17 100644
--- a/lib/Doctrine/Persistence/Mapping/RuntimeReflectionService.php
+++ b/lib/Doctrine/Persistence/Mapping/RuntimeReflectionService.php
@@ -70,7 +70,8 @@ public function getClassNamespace(string $class)
     /**
      * @psalm-param class-string<T> $class
      *
-     * @return ReflectionClass<T>
+     * @return ReflectionClass
+     * @psalm-return ReflectionClass<T>
      *
      * @template T of object
      */
diff --git a/lib/Doctrine/Persistence/Reflection/RuntimePublicReflectionProperty.php b/lib/Doctrine/Persistence/Reflection/RuntimePublicReflectionProperty.php
index 6939d0d0..049abcd4 100644
--- a/lib/Doctrine/Persistence/Reflection/RuntimePublicReflectionProperty.php
+++ b/lib/Doctrine/Persistence/Reflection/RuntimePublicReflectionProperty.php
@@ -44,6 +44,7 @@ public function getValue($object = null)
      * @link https://bugs.php.net/bug.php?id=63463
      *
      * @param object|null $object
+     * @param mixed       $value
      */
     public function setValue($object, $value = null)
     {
diff --git a/lib/Doctrine/Persistence/Reflection/TypedNoDefaultReflectionProperty.php b/lib/Doctrine/Persistence/Reflection/TypedNoDefaultReflectionProperty.php
index bf7d1029..5efb6085 100644
--- a/lib/Doctrine/Persistence/Reflection/TypedNoDefaultReflectionProperty.php
+++ b/lib/Doctrine/Persistence/Reflection/TypedNoDefaultReflectionProperty.php
@@ -20,6 +20,8 @@ class TypedNoDefaultReflectionProperty extends ReflectionProperty
      * Checks that a typed property is initialized before accessing its value.
      * This is necessary to avoid PHP error "Error: Typed property must not be accessed before initialization".
      * Should be used only for reflecting typed properties without a default value.
+     *
+     * @param object|null $object
      */
     public function getValue($object = null)
     {
@@ -45,6 +47,7 @@ public function setValue($object, $value = null)
                 unset($this->$propertyName);
             };
             $unsetter = $unsetter->bindTo($object, $this->getDeclaringClass()->getName());
+            assert($unsetter instanceof Closure);
 
             $unsetter();
 
diff --git a/phpstan.neon b/phpstan.neon
index 9109baea..0647fd61 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -11,7 +11,7 @@ parameters:
         - tests
 
     excludes_analyse:
-        - %currentWorkingDirectory%/tests/Doctrine/Tests/Persistence/Mapping/_files/TestEntity.php
+        - tests/Doctrine/Tests/Persistence/Mapping/_files/TestEntity.php
 
     ignoreErrors:
         - '#Variable property access on \$this\(Doctrine\\Persistence\\Reflection\\TypedNoDefaultReflectionProperty\)\.#'
@@ -33,3 +33,12 @@ parameters:
         -
             message: '#Call to static method PHPUnit\\Framework\\Assert\:\:assertSame\(\) with Symfony\\Component\\Cache\\Adapter\\ArrayAdapter and null will always evaluate to false\.#'
             path: 'tests/Doctrine/Tests/Persistence/Mapping/ClassMetadataFactoryTest.php'
+
+        # https://github.com/phpstan/phpstan/issues/5009
+        -
+            message: '#Call to function assert\(\) with true will always evaluate to true\.#'
+            path: 'lib/Doctrine/Persistence/Reflection/TypedNoDefaultReflectionProperty.php'
+
+        -
+            message: '#Instanceof between Closure\(\)\: void and Closure will always evaluate to true\.#'
+            path: 'lib/Doctrine/Persistence/Reflection/TypedNoDefaultReflectionProperty.php'
diff --git a/tests/Doctrine/Tests/Persistence/Mapping/ClassMetadataFactoryTest.php b/tests/Doctrine/Tests/Persistence/Mapping/ClassMetadataFactoryTest.php
index 473768bf..0ab8b268 100644
--- a/tests/Doctrine/Tests/Persistence/Mapping/ClassMetadataFactoryTest.php
+++ b/tests/Doctrine/Tests/Persistence/Mapping/ClassMetadataFactoryTest.php
@@ -26,12 +26,15 @@
  */
 class ClassMetadataFactoryTest extends DoctrineTestCase
 {
-    /** @var TestClassMetadataFactory<ClassMetadata<object>> */
+    /**
+     * @var TestClassMetadataFactory
+     * @psalm-var TestClassMetadataFactory<ClassMetadata<object>>
+     */
     private $cmf;
 
     protected function setUp(): void
     {
-        $driver    = $this->createMock(MappingDriver::class);
+        $driver = $this->createMock(MappingDriver::class);
 
         /** @psalm-var ClassMetadata<object> */
         $metadata  = $this->createMock(ClassMetadata::class);
diff --git a/tests/Doctrine/Tests/Persistence/Mapping/Fixtures/TestClassMetadata.php b/tests/Doctrine/Tests/Persistence/Mapping/Fixtures/TestClassMetadata.php
index e3ddd2d5..355511b7 100644
--- a/tests/Doctrine/Tests/Persistence/Mapping/Fixtures/TestClassMetadata.php
+++ b/tests/Doctrine/Tests/Persistence/Mapping/Fixtures/TestClassMetadata.php
@@ -46,17 +46,11 @@ public function getReflectionClass(): ReflectionClass
         return new ReflectionClass($this->getName());
     }
 
-    /**
-     * {@inheritDoc}
-     */
     public function isIdentifier(string $fieldName): bool
     {
         return false;
     }
 
-    /**
-     * {@inheritDoc}
-     */
     public function hasField(string $fieldName): bool
     {
         return false;