diff --git a/composer.json b/composer.json
index 4ab0daf5ce683dda69afcad2d72871996d8c20a8..17b108d2c11709028da50b31ca7485206e744d7b 100644
--- a/composer.json
+++ b/composer.json
@@ -7,6 +7,9 @@
 		"nette/di": "~2.4",
 		"nette/bootstrap": "~2.4"
 	},
+	"require-dev": {
+		"phpstan/phpstan-shim": "~0.11.0"
+	},
 	"autoload": {
 		"psr-4": {
 			"Mangoweb\\NetteDIScope\\": "src"
diff --git a/src/ScopeExtension.php b/src/ScopeExtension.php
index 5e07009a6554e389ab9e3b2b2d6c3f3e00b46532..723f36e9d7ca8672f44ad4ccee4a8d51741c7030 100644
--- a/src/ScopeExtension.php
+++ b/src/ScopeExtension.php
@@ -28,8 +28,13 @@ abstract class ScopeExtension extends Nette\DI\CompilerExtension
 
 		$innerContainer = $this->createInnerConfigurator()->createContainer();
 		$innerContainerReflection = new \ReflectionClass($innerContainer);
-		$this->innerContainerClassName = $innerContainerReflection->getName();
-		$this->innerContainerPath = $innerContainerReflection->getFileName();
+
+		$name = $innerContainerReflection->getName();
+		$fileName = $innerContainerReflection->getFileName();
+		assert($fileName !== false);
+
+		$this->innerContainerClassName = $name;
+		$this->innerContainerPath = $fileName;
 
 		$innerContainerDefinition = $builder->addDefinition($this->prefix('container'));
 		$innerContainerDefinition->setType(Nette\DI\Container::class);