diff --git a/.travis.yml b/.travis.yml
index e944b8d..b4a567d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -12,7 +12,6 @@ php:
     - 5.6
     - 7.0
     - 7.1
-    - hhvm
 env:
   global:
     - TEST_COMMAND="composer test"
diff --git a/composer.json b/composer.json
index bfcfb8b..2030510 100644
--- a/composer.json
+++ b/composer.json
@@ -12,17 +12,18 @@
         }
     ],
     "require": {
-        "php": "^5.5 || ^7.0",
+        "php": "^5.6 || ^7.0",
         "php-http/httplug": "^1.0",
         "php-http/client-common": "^1.1",
         "php-http/discovery": "^1.0",
         "webmozart/assert": "^1.2"
     },
     "require-dev": {
-        "phpunit/phpunit": "^4.5 || ^5.4",
+        "phpunit/phpunit": "^5.6",
         "php-http/message-factory": "^1.0.2",
         "php-http/curl-client": "^1.6",
         "php-http/message": "^1.0",
+        "nyholm/nsa": "^1.0",
         "guzzlehttp/psr7": "^1.3"
     },
     "autoload": {
@@ -34,5 +35,10 @@
     "scripts": {
         "test": "vendor/bin/phpunit",
         "test-ci": "vendor/bin/phpunit --coverage-text --coverage-clover=build/coverage.xml"
+    },
+    "extra": {
+        "branch-alias": {
+            "dev-master": "2.0.x-dev"
+        }
     }
 }