diff --git a/src/ExternalLibrary/Definition/DefinitionDiscoveryFactory.php b/src/ExternalLibrary/Definition/DefinitionDiscoveryFactory.php
index 970385e..a3e1074 100644
--- a/src/ExternalLibrary/Definition/DefinitionDiscoveryFactory.php
+++ b/src/ExternalLibrary/Definition/DefinitionDiscoveryFactory.php
@@ -98,6 +98,21 @@ class DefinitionDiscoveryFactory {
       );
     }
 
+    // Add extensions local definition discoveries
+    foreach (['module', 'theme'] as $type) {
+      foreach (array_keys(system_get_info($type)) as $extension) {
+        $extension_path = DRUPAL_ROOT . '/' . drupal_get_path($type, $extension);
+        $extension_definitions = $extension_path . '/library-definitions';
+        if (is_dir($extension_definitions)) {
+          $extension_discovery = new FileDefinitionDiscovery(
+            $this->localSerializer,
+            $extension_definitions
+          );
+          $discovery->addDiscovery($extension_discovery);
+        }
+      }
+    }
+
     return $discovery;
   }