diff --git a/composer.json b/composer.json
index 5300942..22e989c 100644
--- a/composer.json
+++ b/composer.json
@@ -13,7 +13,7 @@
     }],
     "minimum-stability": "dev",
     "require": {
-	"silverstripe/cms": "*",
+	"silverstripe/cms": "^4",
         "dnadesign/silverstripe-elemental": "*",
         "dnadesign/silverstripe-elemental-list": "*",
         "betterbrief/silverstripe-googlemapfield": "*",