diff --git a/composer.json b/composer.json
index c8f92c3..b3abb39 100644
--- a/composer.json
+++ b/composer.json
@@ -11,7 +11,7 @@
     ],
     "bin": ["bin/fetch-mf2", "bin/parse-mf2"],
     "require": {
-        "php": ">=5.4.0"
+        "php": ">=5.6.0"
     },
     "require-dev": {
         "phpunit/phpunit": "4.8.*",