diff --git a/core/lib/Drupal/Component/Plugin/Discovery/AnnotatedClassDiscovery.php b/core/lib/Drupal/Component/Plugin/Discovery/AnnotatedClassDiscovery.php
index 377bf4a..715bbfe 100644
--- a/core/lib/Drupal/Component/Plugin/Discovery/AnnotatedClassDiscovery.php
+++ b/core/lib/Drupal/Component/Plugin/Discovery/AnnotatedClassDiscovery.php
@@ -84,6 +84,8 @@ public function getDefinitions() {
 
     // Search for classes within all PSR-0 namespace locations.
     foreach ($this->getPluginNamespaces() as $namespace => $dirs) {
+      // Extract the module name from this namespace.
+      $module = $this->getModuleFromNamespace($namespace);
       foreach ($dirs as $dir) {
         $dir .= DIRECTORY_SEPARATOR . str_replace('\\', DIRECTORY_SEPARATOR, $namespace);
         if (file_exists($dir)) {
@@ -103,6 +105,7 @@ public function getDefinitions() {
                 // instead of requiring us to work with the annotation object.
                 $definition = $annotation->get();
                 $definition['class'] = $class;
+                $definition['module'] = $module;
                 $definitions[$definition['id']] = $definition;
               }
             }
@@ -114,6 +117,25 @@ public function getDefinitions() {
   }
 
   /**
+   * Extracts a module name from a Drupal namespace.
+   *
+   * @param string $namespace
+   *   The namespace to extract the module name from.
+   *
+   * @return string|null
+   *   The matches module name, or NULL otherwise.
+   */
+  protected function getModuleFromNamespace($namespace) {
+    preg_match('|^Drupal\\\\(?<module>[\w]+)\\\\|', $namespace, $matches);
+
+    if (isset($matches['module'])) {
+      return $matches['module'];
+    }
+
+    return NULL;
+  }
+
+  /**
    * Returns an array of PSR-0 namespaces to search for plugin classes.
    */
   protected function getPluginNamespaces() {