diff --git a/src/ExtraPackage.php b/src/ExtraPackage.php
index 2471cb0..d1c2d30 100644
--- a/src/ExtraPackage.php
+++ b/src/ExtraPackage.php
@@ -114,6 +114,16 @@ public function getMergedRequirements()
         return array_keys($this->mergedRequirements);
     }
 
+    /**
+     * Get the name of this package
+     *
+     * @return string
+     */
+    public function getName()
+    {
+        return $this->json['name'];
+    }
+
     /**
      * Read the contents of a composer.json style file into an array.
      *
diff --git a/src/MergePlugin.php b/src/MergePlugin.php
index a9af5b6..767422a 100644
--- a/src/MergePlugin.php
+++ b/src/MergePlugin.php
@@ -270,6 +270,13 @@ protected function mergeFile(RootPackageInterface $root, $path)
 
         $package = new ExtraPackage($path, $this->composer, $this->logger);
 
+        if (isset($root->getRequires()[$package->getName()])) {
+            $this->logger->info(
+                "Ignoring composer json already required by root: <comment>{$package->getName()}</comment>"
+            );
+            return;
+        }
+
         if (isset($this->loadedNoDev[$path])) {
             $this->logger->info(
                 "Loading -dev sections of <comment>{$path}</comment>..."