diff --git a/.gitignore b/.gitignore
index 3ce5adb..82cfc4e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 .idea
+composer.lock
 vendor
diff --git a/composer.json b/composer.json
index e93a853..5a6c8e6 100644
--- a/composer.json
+++ b/composer.json
@@ -3,8 +3,8 @@
     "description": "Load guzzle service description from various file formats",
     "require": {
         "php": ">=5.5.0",
-        "symfony/config": "~3.0",
-        "symfony/yaml": "~3.0"
+        "symfony/config": "~3.0|^4.0",
+        "symfony/yaml": "~3.0|^4.0"
     },
     "license": "MIT",
     "authors": [
diff --git a/composer.lock b/composer.lock
deleted file mode 100644
index 2e9db00..0000000
--- a/composer.lock
+++ /dev/null
@@ -1,169 +0,0 @@
-{
-    "_readme": [
-        "This file locks the dependencies of your project to a known state",
-        "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
-        "This file is @generated automatically"
-    ],
-    "hash": "950a6c7017df36346b2daebfd6a55cf7",
-    "content-hash": "b19a782dc303a22631422c69ca828fa0",
-    "packages": [
-        {
-            "name": "symfony/config",
-            "version": "v3.0.1",
-            "source": {
-                "type": "git",
-                "url": "https://github.com/symfony/config.git",
-                "reference": "58680a6516a457a6c65044fe33586c4a81fdff01"
-            },
-            "dist": {
-                "type": "zip",
-                "url": "https://api.github.com/repos/symfony/config/zipball/58680a6516a457a6c65044fe33586c4a81fdff01",
-                "reference": "58680a6516a457a6c65044fe33586c4a81fdff01",
-                "shasum": ""
-            },
-            "require": {
-                "php": ">=5.5.9",
-                "symfony/filesystem": "~2.8|~3.0"
-            },
-            "type": "library",
-            "extra": {
-                "branch-alias": {
-                    "dev-master": "3.0-dev"
-                }
-            },
-            "autoload": {
-                "psr-4": {
-                    "Symfony\\Component\\Config\\": ""
-                },
-                "exclude-from-classmap": [
-                    "/Tests/"
-                ]
-            },
-            "notification-url": "https://packagist.org/downloads/",
-            "license": [
-                "MIT"
-            ],
-            "authors": [
-                {
-                    "name": "Fabien Potencier",
-                    "email": "fabien@symfony.com"
-                },
-                {
-                    "name": "Symfony Community",
-                    "homepage": "https://symfony.com/contributors"
-                }
-            ],
-            "description": "Symfony Config Component",
-            "homepage": "https://symfony.com",
-            "time": "2015-12-26 13:39:53"
-        },
-        {
-            "name": "symfony/filesystem",
-            "version": "v3.0.1",
-            "source": {
-                "type": "git",
-                "url": "https://github.com/symfony/filesystem.git",
-                "reference": "c2e59d11dccd135dc8f00ee97f34fe1de842e70c"
-            },
-            "dist": {
-                "type": "zip",
-                "url": "https://api.github.com/repos/symfony/filesystem/zipball/c2e59d11dccd135dc8f00ee97f34fe1de842e70c",
-                "reference": "c2e59d11dccd135dc8f00ee97f34fe1de842e70c",
-                "shasum": ""
-            },
-            "require": {
-                "php": ">=5.5.9"
-            },
-            "type": "library",
-            "extra": {
-                "branch-alias": {
-                    "dev-master": "3.0-dev"
-                }
-            },
-            "autoload": {
-                "psr-4": {
-                    "Symfony\\Component\\Filesystem\\": ""
-                },
-                "exclude-from-classmap": [
-                    "/Tests/"
-                ]
-            },
-            "notification-url": "https://packagist.org/downloads/",
-            "license": [
-                "MIT"
-            ],
-            "authors": [
-                {
-                    "name": "Fabien Potencier",
-                    "email": "fabien@symfony.com"
-                },
-                {
-                    "name": "Symfony Community",
-                    "homepage": "https://symfony.com/contributors"
-                }
-            ],
-            "description": "Symfony Filesystem Component",
-            "homepage": "https://symfony.com",
-            "time": "2015-12-22 10:39:06"
-        },
-        {
-            "name": "symfony/yaml",
-            "version": "v3.0.1",
-            "source": {
-                "type": "git",
-                "url": "https://github.com/symfony/yaml.git",
-                "reference": "3df409958a646dad2bc5046c3fb671ee24a1a691"
-            },
-            "dist": {
-                "type": "zip",
-                "url": "https://api.github.com/repos/symfony/yaml/zipball/3df409958a646dad2bc5046c3fb671ee24a1a691",
-                "reference": "3df409958a646dad2bc5046c3fb671ee24a1a691",
-                "shasum": ""
-            },
-            "require": {
-                "php": ">=5.5.9"
-            },
-            "type": "library",
-            "extra": {
-                "branch-alias": {
-                    "dev-master": "3.0-dev"
-                }
-            },
-            "autoload": {
-                "psr-4": {
-                    "Symfony\\Component\\Yaml\\": ""
-                },
-                "exclude-from-classmap": [
-                    "/Tests/"
-                ]
-            },
-            "notification-url": "https://packagist.org/downloads/",
-            "license": [
-                "MIT"
-            ],
-            "authors": [
-                {
-                    "name": "Fabien Potencier",
-                    "email": "fabien@symfony.com"
-                },
-                {
-                    "name": "Symfony Community",
-                    "homepage": "https://symfony.com/contributors"
-                }
-            ],
-            "description": "Symfony Yaml Component",
-            "homepage": "https://symfony.com",
-            "time": "2015-12-26 13:39:53"
-        }
-    ],
-    "packages-dev": [],
-    "aliases": [],
-    "minimum-stability": "stable",
-    "stability-flags": [],
-    "prefer-stable": false,
-    "prefer-lowest": false,
-    "platform": {
-        "php": ">=5.5.0"
-    },
-    "platform-dev": []
-}
diff --git a/src/FileLoader.php b/src/FileLoader.php
index 6a7f2bf..8c2fe69 100644
--- a/src/FileLoader.php
+++ b/src/FileLoader.php
@@ -31,10 +31,9 @@ public function load($resource, $type = null)
             foreach($configValues["imports"] as $file) {
                 $configValues = array_merge_recursive($configValues, $this->import($this->locator->locate($file)));
             }
+            unset($configValues["imports"]);
         }
 
-        unset($configValues["imports"]);
-
         return $configValues;
     }
 
diff --git a/tests/fixtures/invalid.yml b/tests/fixtures/invalid.yml
index 194ae3d..e0f0559 100644
--- a/tests/fixtures/invalid.yml
+++ b/tests/fixtures/invalid.yml
@@ -1,2 +1,2 @@
-operations
-    certificates.add:
\ No newline at end of file
+operations:
+-certificates.add
\ No newline at end of file