diff --git a/Schemas/visinfo.xsd b/Schemas/visinfo.xsd
index bfa4e0f6..06312b06 100644
--- a/Schemas/visinfo.xsd
+++ b/Schemas/visinfo.xsd
@@ -49,6 +49,8 @@
 					</xs:complexType>
 				</xs:element>
 			</xs:sequence>
+			<!-- Guid of the viewpoint -->
+			<xs:attribute name="Guid" type="Guid" use="required"/>
 		</xs:complexType>
 	</xs:element>
 	<xs:complexType name="OrthogonalCamera">
@@ -130,4 +132,9 @@
 			<xs:enumeration value="JPG"/>
 		</xs:restriction>
 	</xs:simpleType>
+	<xs:simpleType name="Guid">
+		<xs:restriction base="xs:string">
+			<xs:pattern value="[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{12}"/>
+		</xs:restriction>
+	</xs:simpleType>
 </xs:schema>