diff --git a/composer.json b/composer.json
index b4e21a7..302e731 100644
--- a/composer.json
+++ b/composer.json
@@ -21,7 +21,7 @@
 	"minimum-stability": "dev",
 	"require": {
 		"php": ">=5.3.3",
-		"swiftmailer/swiftmailer": ">=4.0",
+		"swiftmailer/swiftmailer": "~4.0||~5.0",
 		"composer/installers": "^1.0",
 		"aimeos/aimeos-core": "~2016.10"
 	},