diff --git a/src/MAPI/Property/PropertyStore.php b/src/MAPI/Property/PropertyStore.php
index 5cdd158..f4102f0 100644
--- a/src/MAPI/Property/PropertyStore.php
+++ b/src/MAPI/Property/PropertyStore.php
@@ -152,6 +152,8 @@ protected function parseNameId($obj)
 
             //# a bit sus
             $guid_off = $flags >> 1;
+            if (!isset($guids[$guid_off - 2]))
+                return;
             $guid = $guids[$guid_off - 2];
 
             /*$properties[] = [