diff --git a/composer.json b/composer.json
index e71bcc6cc..9f582536b 100644
--- a/composer.json
+++ b/composer.json
@@ -33,8 +33,8 @@
         "monolog/monolog": "^1.16",
         "nikic/php-parser": "^4.10.5",
         "psr/container": "^1",
-        "silverstripe/config": "^1@dev",
-        "silverstripe/assets": "^1@dev",
+        "silverstripe/config": "1.6.x-dev",
+        "silverstripe/assets": "1.13.x-dev",
         "silverstripe/vendor-plugin": "^1.6",
         "sminnee/callbacklist": "^0.1",
         "swiftmailer/swiftmailer": "^6.2",
@@ -115,4 +115,4 @@
     },
     "minimum-stability": "dev",
     "prefer-stable": true
-}
+}
\ No newline at end of file