diff --git a/composer.json b/composer.json
index 7a97a47995..8885552fdb 100644
--- a/composer.json
+++ b/composer.json
@@ -14,7 +14,8 @@
     "prefer-stable": true,
     "config": {
         "preferred-install": "dist",
-        "autoloader-suffix": "Drupal8"
+        "autoloader-suffix": "Drupal8",
+        "platform": {"php": "5.6"}
     },
     "extra": {
         "_readme": [