diff --git a/composer.json b/composer.json
index 93e344d..b6ddb2c 100644
--- a/composer.json
+++ b/composer.json
@@ -6,6 +6,9 @@
     "psr-4": {
     }
   },
+  "license": [
+    "GPL-3.0-or-later"
+  ],
   "minimum-stability": "dev",
   "require": {
     "horstoeko/zugferd": "^1.0",