diff --git a/composer.json b/composer.json
index 46c16323..e7fa293a 100644
--- a/composer.json
+++ b/composer.json
@@ -29,7 +29,12 @@
     "require-dev": {
         "phpunit/phpunit": "^5.7"
     },
-    "extra": [],
+    "extra": {
+        "branch-alias": {
+            "4.x-dev": "4.0.x-dev",
+            "dev-master": "5.x-dev"
+        }
+    },
     "autoload": {
         "psr-4": {
             "SilverStripe\\Reports\\": "code/",