diff --git a/composer.json b/composer.json
index 2d82a02..9cad250 100644
--- a/composer.json
+++ b/composer.json
@@ -5,9 +5,7 @@
     "homepage": "https://github.com/prawnsalad/Nexmo-PHP-lib",
     "license": "MIT",
     "autoload": {
-        "psr-4": {
-            "PrawnSalad\\Nexmo\\": ["src"]
-        }
+        "classmap": ["src/"]
     }
 }