diff --git a/composer.json b/composer.json
index e9f9166..aec5485 100644
--- a/composer.json
+++ b/composer.json
@@ -19,7 +19,7 @@
   "require-dev": {
     "composer/composer": "1.6.3",
     "consolidation/robo": "1.2.3",
-    "phpunit/phpunit": "6.5.4",
+    "phpunit/phpunit": "6.5.8",
     "sensiolabs/security-checker": "^4.0"
   },
   "autoload": {
diff --git a/composer.lock b/composer.lock
index fe17985..952b959 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
         "This file is @generated automatically"
     ],
-    "content-hash": "52901c9a1e5c2288f5b42dd7ad92fcd1",
+    "content-hash": "6612a15df7d78601fdf04346f975ec2c",
     "packages": [],
     "packages-dev": [
         {
@@ -1528,16 +1528,16 @@
         },
         {
             "name": "phpunit/phpunit",
-            "version": "6.5.4",
+            "version": "6.5.8",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/phpunit.git",
-                "reference": "1b2f933d5775f9237369deaa2d2bfbf9d652be4c"
+                "reference": "4f21a3c6b97c42952fd5c2837bb354ec0199b97b"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/sebastianbergmann/phpunit/zipball/1b2f933d5775f9237369deaa2d2bfbf9d652be4c",
-                "reference": "1b2f933d5775f9237369deaa2d2bfbf9d652be4c",
+                "url": "https://api.github.com/repos/sebastianbergmann/phpunit/zipball/4f21a3c6b97c42952fd5c2837bb354ec0199b97b",
+                "reference": "4f21a3c6b97c42952fd5c2837bb354ec0199b97b",
                 "shasum": ""
             },
             "require": {
@@ -1608,7 +1608,7 @@
                 "testing",
                 "xunit"
             ],
-            "time": "2017-12-10T08:06:19+00:00"
+            "time": "2018-04-10T11:38:34+00:00"
         },
         {
             "name": "phpunit/phpunit-mock-objects",