diff --git a/src/applications/nuance/source/NuanceSourceDefinition.php b/src/applications/nuance/source/NuanceSourceDefinition.php
--- a/src/applications/nuance/source/NuanceSourceDefinition.php
+++ b/src/applications/nuance/source/NuanceSourceDefinition.php
@@ -206,7 +206,7 @@
     return new Aphront404Response();
   }
 
-  public function getActionURI($path = null) {
+  public function getActionURI($path = '') {
     $source_id = $this->getSource()->getID();
     return '/action/'.$source_id.'/'.ltrim($path, '/');
   }