diff --git a/src/HelpScout/model/Conversation.php b/src/HelpScout/model/Conversation.php
index <HASH>..<HASH> 100644
--- a/src/HelpScout/model/Conversation.php
+++ b/src/HelpScout/model/Conversation.php
@@ -77,7 +77,7 @@ class Conversation {
 			$this->bccList     = isset($data->bcc) ? $data->bcc : null;
 			$this->tags        = isset($data->tags) ? $data->tags : null;
 
-			if ($data->closedBy) {
+			if (isset($data->closedBy)) {
 				$this->closedBy = new \HelpScout\model\ref\PersonRef($data->closedBy);
 			}
Add an `isset` wrapper around the `$data->closedBy` in `Conversation` to avoid errors