diff --git a/composer.json b/composer.json
index e09b417..d1a58cd 100644
--- a/composer.json
+++ b/composer.json
@@ -10,7 +10,8 @@
     },
     "require-dev": {
         "phpunit/phpunit": "4.3.5",
-        "satooshi/php-coveralls": ">=0.6.1"
+        "satooshi/php-coveralls": ">=0.6.1",
+        "malkusch/php-mock": "dev-php-5.3"
     },
     "autoload": {
         "psr-4": {