diff --git a/src/Plugin.php b/src/Plugin.php
index 9f966a4..84c69f3 100644
--- a/src/Plugin.php
+++ b/src/Plugin.php
@@ -156,7 +156,9 @@ public function processPackage(PackageInterface $package)
         );
 
         if (isset($files['defines'])) {
-            $this->readConfigFile($package, $files['defines']);
+            foreach ((array) $files['defines'] as $file) {
+                $this->readConfigFile($package, $file);
+            }
             unset($files['defines']);
         }