diff --git a/addressbook/inc/class.addressbook_groupdav.inc.php b/addressbook/inc/class.addressbook_groupdav.inc.php
index 9bd7c7dec2..019abb26d2 100644
--- a/addressbook/inc/class.addressbook_groupdav.inc.php
+++ b/addressbook/inc/class.addressbook_groupdav.inc.php
@@ -1108,6 +1108,11 @@ class addressbook_groupdav extends Api\CalDAV\Handler
 				$keys['id'] = $id;
 			}
 		}
+		// json with uid
+		elseif (empty(self::$path_extension) && (string)$id !== (string)(int)$id)
+		{
+			$keys['uid'] = $id;
+		}
 		else
 		{
 			$keys[self::$path_attr] = $id;
diff --git a/doc/REST-CalDAV-CardDAV/README.md b/doc/REST-CalDAV-CardDAV/README.md
index d203c94df5..aae51ee955 100644
--- a/doc/REST-CalDAV-CardDAV/README.md
+++ b/doc/REST-CalDAV-CardDAV/README.md
@@ -278,6 +278,60 @@ Location: https://example.org/egroupware/groupdav.php/<username>/addressbook/123
 
 * **PUT**  requests with  a ```Content-Type: application/json``` header allow modifying single resources (requires to specify all attributes!)
 
+<details>
+   <summary>Example: PUT request to update a resource</summary>
+
+```
+cat <<EOF | curl -i 'https://example.org/egroupware/groupdav.php/<username>/addressbook/1234' -X PUT -d @- -H "Content-Type: application/json" --user <username>
+{
+  "uid": "5638-8623c4830472a8ede9f9f8b30d435ea4",
+  "prodId": "EGroupware Addressbook 21.1.001",
+  "created": "2010-10-21T09:55:42Z",
+  "updated": "2014-06-02T14:45:24Z",
+  "name": [
+    { "type": "@type": "NameComponent", "personal", "value": "Default" },
+    { "type": "@type": "NameComponent", "surname", "value": "Tester" }
+  ],
+  "fullName": { "value": "Default Tester" },
+....
+}
+EOF
+
+HTTP/1.1 204 No Content
+```
+</details>
+
+<details>
+   <summary>Example: PUT request with UID to update an existing resource or create it, if not exists</summary>
+
+```
+cat <<EOF | curl -i 'https://example.org/egroupware/groupdav.php/<username>/addressbook/5638-8623c4830472a8ede9f9f8b30d435ea4' -X PUT -d @- -H "Content-Type: application/json" --user <username>
+{
+  "uid": "5638-8623c4830472a8ede9f9f8b30d435ea4",
+  "prodId": "EGroupware Addressbook 21.1.001",
+  "created": "2010-10-21T09:55:42Z",
+  "updated": "2014-06-02T14:45:24Z",
+  "name": [
+    { "type": "@type": "NameComponent", "personal", "value": "Default" },
+    { "type": "@type": "NameComponent", "surname", "value": "Tester" }
+  ],
+  "fullName": { "value": "Default Tester" },
+....
+}
+EOF
+```
+Update of an existing one:
+```
+HTTP/1.1 204 No Content
+```
+New contact:
+```
+HTTP/1.1 201 Created
+Location: https://example.org/egroupware/groupdav.php/<username>/addressbook/1234
+```
+</details>
+
+
 * **PATCH** request with a ```Content-Type: application/json``` header allow to modify a single resource by only specifying changed attributes as a [PatchObject](https://www.rfc-editor.org/rfc/rfc8984.html#type-PatchObject)
 
 <details>