diff --git a/composer.json b/composer.json
index 48d1271..86d07f7 100644
--- a/composer.json
+++ b/composer.json
@@ -19,7 +19,7 @@
 	"require-dev": {
 		"symfony/var-dumper": "~3.1.0",
 		"squizlabs/php_codesniffer": "~2.6.2",
-		"phpunit/phpunit": "~5.4.8"
+		"phpunit/phpunit": "~5.5.2"
 	},
 	"extra": {
 		"paas": {
diff --git a/composer.lock b/composer.lock
index a1d77f2..e3e9f9c 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,8 +4,8 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
         "This file is @generated automatically"
     ],
-    "hash": "3161cca7432009f93c6a6c5d06d69669",
-    "content-hash": "d8d65bca7181cfc0a498f511629d165d",
+    "hash": "9c4657008fcebce7e45807ae0dc59d30",
+    "content-hash": "054a8bdbb08cfac744d4b28965fb6f17",
     "packages": [
         {
             "name": "container-interop/container-interop",
@@ -1253,16 +1253,16 @@
         },
         {
             "name": "phpunit/phpunit",
-            "version": "5.4.8",
+            "version": "5.5.2",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/phpunit.git",
-                "reference": "3132365e1430c091f208e120b8845d39c25f20e6"
+                "reference": "46ec2d1522ae8c9a12aca6b7650e0be78bbb0502"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/sebastianbergmann/phpunit/zipball/3132365e1430c091f208e120b8845d39c25f20e6",
-                "reference": "3132365e1430c091f208e120b8845d39c25f20e6",
+                "url": "https://api.github.com/repos/sebastianbergmann/phpunit/zipball/46ec2d1522ae8c9a12aca6b7650e0be78bbb0502",
+                "reference": "46ec2d1522ae8c9a12aca6b7650e0be78bbb0502",
                 "shasum": ""
             },
             "require": {
@@ -1301,7 +1301,7 @@
             "type": "library",
             "extra": {
                 "branch-alias": {
-                    "dev-master": "5.4.x-dev"
+                    "dev-master": "5.5.x-dev"
                 }
             },
             "autoload": {
@@ -1327,7 +1327,7 @@
                 "testing",
                 "xunit"
             ],
-            "time": "2016-07-26 14:48:00"
+            "time": "2016-08-18 11:10:44"
         },
         {
             "name": "phpunit/phpunit-mock-objects",