diff --git a/src/model/property_catalogue.rs b/src/model/property_catalogue.rs
index 2f4a926..77ffb68 100644
--- a/src/model/property_catalogue.rs
+++ b/src/model/property_catalogue.rs
@@ -41,7 +41,8 @@ pub struct PropertyCatalogue {
     #[serde(rename = "SID")]
     sid: String,
     #[serde(rename = "GUID")]
-    guid: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    guid: Option<String>,
     #[serde(rename = "Revision")]
     revision: u16,
     #[serde(rename = "Versions")]