diff --git a/composer.json b/composer.json
index b0e05dc98..59646d5e4 100644
--- a/composer.json
+++ b/composer.json
@@ -19,8 +19,7 @@
     },
     "require": {
         "php": ">=5.2.8",
-        "ext-mcrypt": "*",
-        "ext-mbstring": "*"
+        "ext-mcrypt": "*"
     },
     "require-dev": {
         "phpunit/phpunit": "3.7.*",