diff --git a/lib/ProxyClassFactory.php b/lib/ProxyClassFactory.php
index 598e2ec..52a6a6e 100644
--- a/lib/ProxyClassFactory.php
+++ b/lib/ProxyClassFactory.php
@@ -63,7 +63,7 @@ private static function buildMethods(array $methods): string
     {
         $publicStringMethods = array();
         foreach ($methods as $method) {
-            if (false !== strpos($method->getName(), '__')) {
+            if (false !== strpos($method->getName(), '__construct')) {
                 continue;
             }
 
@@ -132,7 +132,14 @@ private static function buildParameterDefaultValue(ReflectionParameter $paramete
 
         $defaultValue = '=';
         if ($parameter->isDefaultValueConstant()) {
-            $defaultValue .= '\\'.$parameter->getDefaultValueConstantName();
+            $defaultValueConstantName = $parameter->getDefaultValueConstantName();
+            list($type) = explode('::', $defaultValueConstantName);
+
+            if (!\in_array($type, array('self', 'static'))) {
+                $defaultValue .= '\\';
+            }
+
+            $defaultValue .= $defaultValueConstantName;
 
             return $defaultValue;
         }
diff --git a/tests/Dummy.php b/tests/Dummy.php
index 1291a92..01f2122 100644
--- a/tests/Dummy.php
+++ b/tests/Dummy.php
@@ -6,6 +6,8 @@
 
 class Dummy
 {
+    const SOME_VALUE = 'dummy-value';
+
     public function hello(): string
     {
         return 'hello';
diff --git a/tests/InstanceSpy.php b/tests/InstanceSpy.php
new file mode 100644
index 0000000..756c991
--- /dev/null
+++ b/tests/InstanceSpy.php
@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Golossus\LazyProxyLoading\Tests;
+
+class InstanceSpy
+{
+    private $method;
+    private $input;
+
+    /**
+     * InstanceSpy constructor.
+     */
+    public function __construct()
+    {
+    }
+
+    public function setVars($method, $input = null)
+    {
+        $this->method = $method;
+        $this->input = $input;
+    }
+
+    /**
+     * @return mixed
+     */
+    public function getMethod()
+    {
+        return $this->method;
+    }
+
+    /**
+     * @return mixed
+     */
+    public function getInput()
+    {
+        return $this->input;
+    }
+}
diff --git a/tests/ProxyClassFactoryTest.php b/tests/ProxyClassFactoryTest.php
index fbe343d..9438f9d 100644
--- a/tests/ProxyClassFactoryTest.php
+++ b/tests/ProxyClassFactoryTest.php
@@ -12,70 +12,79 @@ class ProxyClassFactoryTest extends TestCase
     public function testCreate()
     {
         /** @var TestSpy $proxy */
-        $proxy = ProxyClassFactory::create(TestSpy::class, function () {
-            return new TestSpy();
+        $instanceSpy = new InstanceSpy();
+        $proxy = ProxyClassFactory::create(TestSpy::class, function () use ($instanceSpy) {
+            return new TestSpy($instanceSpy);
         });
 
         $this->assertInstanceOf(TestSpy::class, $proxy);
 
         $proxy->noReturnType();
-        $this->assertEquals('noReturnType', $proxy::$method);
-        $this->assertNull($proxy::$input);
+        $this->assertEquals('noReturnType', $instanceSpy->getMethod());
+        $this->assertNull($instanceSpy->getInput());
 
         $proxy->voidReturnType();
-        $this->assertEquals('voidReturnType', $proxy::$method);
-        $this->assertNull($proxy::$input);
+        $this->assertEquals('voidReturnType', $instanceSpy->getMethod());
+        $this->assertNull($instanceSpy->getInput());
 
         $output = $proxy->nullableBuiltInReturnType();
-        $this->assertEquals('nullableBuiltInReturnType', $proxy::$method);
-        $this->assertNull($proxy::$input);
+        $this->assertEquals('nullableBuiltInReturnType', $instanceSpy->getMethod());
+        $this->assertNull($instanceSpy->getInput());
         $this->assertEquals($output, 1);
 
         $output = $proxy->notNullableBuiltInReturnType();
-        $this->assertEquals('notNullableBuiltInReturnType', $proxy::$method);
-        $this->assertNull($proxy::$input);
+        $this->assertEquals('notNullableBuiltInReturnType', $instanceSpy->getMethod());
+        $this->assertNull($instanceSpy->getInput());
         $this->assertEquals($output, true);
 
         $output = $proxy->notNullableNotBuiltInReturnType();
-        $this->assertEquals('notNullableNotBuiltInReturnType', $proxy::$method);
-        $this->assertNull($proxy::$input);
+        $this->assertEquals('notNullableNotBuiltInReturnType', $instanceSpy->getMethod());
+        $this->assertNull($instanceSpy->getInput());
         $this->assertEquals($output, new Dummy());
 
         $output = $proxy->nullableNotBuiltInReturnType();
-        $this->assertEquals('nullableNotBuiltInReturnType', $proxy::$method);
-        $this->assertNull($proxy::$input);
+        $this->assertEquals('nullableNotBuiltInReturnType', $instanceSpy->getMethod());
+        $this->assertNull($instanceSpy->getInput());
         $this->assertEquals($output, new Dummy());
 
         $proxy->noTypeHintingParamType(10);
-        $this->assertEquals('noTypeHintingParamType', $proxy::$method);
-        $this->assertEquals(10, $proxy::$input);
+        $this->assertEquals('noTypeHintingParamType', $instanceSpy->getMethod());
+        $this->assertEquals(10, $instanceSpy->getInput());
 
         $proxy->nullableBuiltInParamType(null);
-        $this->assertEquals('nullableBuiltInParamType', $proxy::$method);
-        $this->assertNull($proxy::$input);
+        $this->assertEquals('nullableBuiltInParamType', $instanceSpy->getMethod());
+        $this->assertNull($instanceSpy->getInput());
 
         $proxy->notNullableBuiltInParamType(true);
-        $this->assertEquals('notNullableBuiltInParamType', $proxy::$method);
-        $this->assertTrue($proxy::$input);
+        $this->assertEquals('notNullableBuiltInParamType', $instanceSpy->getMethod());
+        $this->assertTrue($instanceSpy->getInput());
 
         $proxy->notNullableNotBuiltInParamType(new Dummy());
-        $this->assertEquals('notNullableNotBuiltInParamType', $proxy::$method);
-        $this->assertEquals(new Dummy(), $proxy::$input);
+        $this->assertEquals('notNullableNotBuiltInParamType', $instanceSpy->getMethod());
+        $this->assertEquals(new Dummy(), $instanceSpy->getInput());
 
         $proxy->nullableNotBuiltInParamType(null);
-        $this->assertEquals('nullableNotBuiltInParamType', $proxy::$method);
-        $this->assertNull($proxy::$input);
+        $this->assertEquals('nullableNotBuiltInParamType', $instanceSpy->getMethod());
+        $this->assertNull($instanceSpy->getInput());
 
         $proxy->nullableDefaultParamType();
-        $this->assertEquals('nullableDefaultParamType', $proxy::$method);
-        $this->assertNull($proxy::$input);
+        $this->assertEquals('nullableDefaultParamType', $instanceSpy->getMethod());
+        $this->assertNull($instanceSpy->getInput());
 
         $proxy->notNullableDefaultParamType();
-        $this->assertEquals('notNullableDefaultParamType', $proxy::$method);
-        $this->assertEquals(10, $proxy::$input);
+        $this->assertEquals('notNullableDefaultParamType', $instanceSpy->getMethod());
+        $this->assertEquals(10, $instanceSpy->getInput());
+
+        $proxy->notNullableExternalConstantDefaultParamType();
+        $this->assertEquals('notNullableExternalConstantDefaultParamType', $instanceSpy->getMethod());
+        $this->assertEquals(Dummy::SOME_VALUE, $instanceSpy->getInput());
+
+        $proxy->notNullableSelfConstantDefaultParamType();
+        $this->assertEquals('notNullableSelfConstantDefaultParamType', $instanceSpy->getMethod());
+        $this->assertEquals($proxy::SOME_VALUE, $instanceSpy->getInput());
 
         $proxy->paramList(10, null, true, new Dummy(), null, new Dummy());
-        $this->assertEquals('paramList', $proxy::$method);
+        $this->assertEquals('paramList', $instanceSpy->getMethod());
         $this->assertEquals(array(
             10,
             null,
@@ -84,13 +93,21 @@ public function testCreate()
             null,
             new Dummy(),
             10,
-        ), $proxy::$input);
+        ), $instanceSpy->getInput());
 
         $callable = function () {
             return 10;
         };
         $proxy->withCallableParameter($callable);
-        $this->assertEquals('withCallableParameter', $proxy::$method);
-        $this->assertEquals($callable(), ($proxy::$input)());
+        $this->assertEquals('withCallableParameter', $instanceSpy->getMethod());
+        $this->assertEquals($callable(), ($instanceSpy->getInput())());
+
+        $proxy();
+        $this->assertEquals('__invoke', $instanceSpy->getMethod());
+        $this->assertNull($instanceSpy->getInput());
+
+        $clonedProxy = clone $proxy;
+        $this->assertEquals('__clone', $instanceSpy->getMethod());
+        $this->assertNull($instanceSpy->getInput());
     }
 }
diff --git a/tests/TestSpy.php b/tests/TestSpy.php
index ca42ed6..5e25b9b 100644
--- a/tests/TestSpy.php
+++ b/tests/TestSpy.php
@@ -6,95 +6,121 @@
 
 class TestSpy
 {
-    public static $method;
-    public static $input;
+    const SOME_VALUE = 'self-value';
 
-    private static function setVars($method, $input = null)
+    /**
+     * @var InstanceSpy
+     */
+    private $instanceSpy;
+
+    /**
+     * TestSpy constructor.
+     */
+    public function __construct(InstanceSpy $instanceSpy)
     {
-        static::$method = $method;
-        static::$input = $input;
+        $this->instanceSpy = $instanceSpy;
     }
 
     public function noReturnType()
     {
-        static::setVars('noReturnType');
+        $this->instanceSpy->setVars('noReturnType');
     }
 
     public function voidReturnType(): void
     {
-        static::setVars('voidReturnType');
+        $this->instanceSpy->setVars('voidReturnType');
     }
 
     public function nullableBuiltInReturnType(): ?int
     {
-        static::setVars('nullableBuiltInReturnType');
+        $this->instanceSpy->setVars('nullableBuiltInReturnType');
 
         return 1;
     }
 
     public function notNullableBuiltInReturnType(): bool
     {
-        static::setVars('notNullableBuiltInReturnType');
+        $this->instanceSpy->setVars('notNullableBuiltInReturnType');
 
         return true;
     }
 
     public function notNullableNotBuiltInReturnType(): Dummy
     {
-        static::setVars('notNullableNotBuiltInReturnType');
+        $this->instanceSpy->setVars('notNullableNotBuiltInReturnType');
 
         return new Dummy();
     }
 
     public function nullableNotBuiltInReturnType(): ?Dummy
     {
-        static::setVars('nullableNotBuiltInReturnType');
+        $this->instanceSpy->setVars('nullableNotBuiltInReturnType');
 
         return new Dummy();
     }
 
     public function noTypeHintingParamType($value)
     {
-        static::setVars('noTypeHintingParamType', $value);
+        $this->instanceSpy->setVars('noTypeHintingParamType', $value);
     }
 
     public function nullableBuiltInParamType(?int $value)
     {
-        static::setVars('nullableBuiltInParamType', $value);
+        $this->instanceSpy->setVars('nullableBuiltInParamType', $value);
     }
 
     public function notNullableBuiltInParamType(bool $value)
     {
-        static::setVars('notNullableBuiltInParamType', $value);
+        $this->instanceSpy->setVars('notNullableBuiltInParamType', $value);
     }
 
     public function notNullableNotBuiltInParamType(Dummy $value)
     {
-        static::setVars('notNullableNotBuiltInParamType', $value);
+        $this->instanceSpy->setVars('notNullableNotBuiltInParamType', $value);
     }
 
     public function nullableNotBuiltInParamType(?Dummy $value)
     {
-        static::setVars('nullableNotBuiltInParamType', $value);
+        $this->instanceSpy->setVars('nullableNotBuiltInParamType', $value);
     }
 
     public function nullableDefaultParamType(?Dummy $juan = null)
     {
-        static::setVars('nullableDefaultParamType', $juan);
+        $this->instanceSpy->setVars('nullableDefaultParamType', $juan);
     }
 
     public function notNullableDefaultParamType(int $value = 10)
     {
-        static::setVars('notNullableDefaultParamType', $value);
+        $this->instanceSpy->setVars('notNullableDefaultParamType', $value);
+    }
+
+    public function notNullableExternalConstantDefaultParamType(string $value = Dummy::SOME_VALUE)
+    {
+        $this->instanceSpy->setVars('notNullableExternalConstantDefaultParamType', $value);
+    }
+
+    public function notNullableSelfConstantDefaultParamType(string $value = self::SOME_VALUE)
+    {
+        $this->instanceSpy->setVars('notNullableSelfConstantDefaultParamType', $value);
     }
 
     public function paramList($value1, ?int $value2, bool $value3, Dummy $value4, ?Dummy $value5, ?Dummy $value6 = null, int $value7 = 10)
     {
-        static::setVars('paramList', \func_get_args());
+        $this->instanceSpy->setVars('paramList', \func_get_args());
     }
 
     public function withCallableParameter(callable $param)
     {
-        static::setVars('withCallableParameter', $param);
+        $this->instanceSpy->setVars('withCallableParameter', $param);
+    }
+
+    public function __invoke()
+    {
+        $this->instanceSpy->setVars('__invoke');
+    }
+
+    public function __clone()
+    {
+        $this->instanceSpy->setVars('__clone');
     }
 }