diff --git a/composer.json b/composer.json
index 3c2da02..4e60dbe 100644
--- a/composer.json
+++ b/composer.json
@@ -25,7 +25,7 @@
         }
     ],
     "require":           {
-        "php":                      "^5.5 || ^7.0",
+        "php":                      "^5.6 || ^7.0",
         "psr/cache":                "^1.0",
         "psr/simple-cache":         "^1.0",
         "cache/adapter-common":     "^0.4",