diff --git a/composer.json b/composer.json
index 9b153194..bc14c439 100644
--- a/composer.json
+++ b/composer.json
@@ -34,7 +34,7 @@
         "aws/aws-sdk-php": "Allow sending log messages to AWS services like DynamoDB"
     },
     "autoload": {
-        "psr-0": {"Monolog": "src/"}
+        "psr-4": {"Monolog\\": "src/Monolog"}
     },
     "extra": {
         "branch-alias": {
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
index 05e49eda..b78740e2 100644
--- a/tests/bootstrap.php
+++ b/tests/bootstrap.php
@@ -10,6 +10,6 @@
  */
 
 $loader = require __DIR__ . "/../vendor/autoload.php";
-$loader->add('Monolog\\', __DIR__);
+$loader->addPsr4('Monolog\\', __DIR__.'/Monolog');
 
 date_default_timezone_set('UTC');