diff --git a/composer.json b/composer.json
index 5b913605..fc821863 100644
--- a/composer.json
+++ b/composer.json
@@ -14,7 +14,8 @@
 		}
 	],
 	"require": {
-		"php": ">=5.2.0"
+		"php": ">=5.2.0",
+		"ext-json": "*"
 	},
 	"autoload": {
 		"files": ["load-v4p8.php"]