diff --git a/composer.lock b/composer.lock
index d84dfe6..ffab9cf 100644
--- a/composer.lock
+++ b/composer.lock
@@ -8,26 +8,27 @@
     "packages": [
         {
             "name": "amphp/amp",
-            "version": "v2.1.1",
+            "version": "v2.3.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/amphp/amp.git",
-                "reference": "7075ef7d74dbd32626bfd31c976b23055c3ade6a"
+                "reference": "5a294f13810844e3bdda28c0f352821d735ca9b3"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/amphp/amp/zipball/7075ef7d74dbd32626bfd31c976b23055c3ade6a",
-                "reference": "7075ef7d74dbd32626bfd31c976b23055c3ade6a",
+                "url": "https://api.github.com/repos/amphp/amp/zipball/5a294f13810844e3bdda28c0f352821d735ca9b3",
+                "reference": "5a294f13810844e3bdda28c0f352821d735ca9b3",
                 "shasum": ""
             },
             "require": {
                 "php": ">=7"
             },
             "require-dev": {
+                "amphp/php-cs-fixer-config": "dev-master",
                 "amphp/phpunit-util": "^1",
-                "friendsofphp/php-cs-fixer": "^2.3",
+                "ext-json": "*",
                 "phpstan/phpstan": "^0.8.5",
-                "phpunit/phpunit": "^6.0.9",
+                "phpunit/phpunit": "^6.0.9 | ^7",
                 "react/promise": "^2"
             },
             "type": "library",
@@ -50,14 +51,6 @@
                 "MIT"
             ],
             "authors": [
-                {
-                    "name": "Bob Weinand",
-                    "email": "bobwei9@hotmail.com"
-                },
-                {
-                    "name": "Niklas Keller",
-                    "email": "me@kelunik.com"
-                },
                 {
                     "name": "Daniel Lowrey",
                     "email": "rdlowrey@php.net"
@@ -65,6 +58,14 @@
                 {
                     "name": "Aaron Piotrowski",
                     "email": "aaron@trowski.com"
+                },
+                {
+                    "name": "Bob Weinand",
+                    "email": "bobwei9@hotmail.com"
+                },
+                {
+                    "name": "Niklas Keller",
+                    "email": "me@kelunik.com"
                 }
             ],
             "description": "A non-blocking concurrency framework for PHP applications.",
@@ -80,7 +81,7 @@
                 "non-blocking",
                 "promise"
             ],
-            "time": "2018-12-11T10:31:37+00:00"
+            "time": "2019-10-01T19:39:23+00:00"
         },
         {
             "name": "amphp/artax",