diff --git a/composer.json b/composer.json
index cfb71517..d2dc2ad3 100644
--- a/composer.json
+++ b/composer.json
@@ -17,7 +17,7 @@
     },
     "require-dev": {
         "cerdic/css-tidy": "^1.7 || ^2.0",
-        "simpletest/simpletest": "dev-master"
+        "simpletest/simpletest": "^1.3"
     },
     "autoload": {
         "psr-0": { "HTMLPurifier": "library/" },