diff --git a/src/eCH-0261-1-0.xsd b/src/eCH-0261-1-0.xsd
index 08cb1fa..e4aab2b 100644
--- a/src/eCH-0261-1-0.xsd
+++ b/src/eCH-0261-1-0.xsd
@@ -308,6 +308,7 @@ Datum				Version				Autor
 				</xs:annotation>
 				<xs:simpleType>
 					<xs:restriction base="xs:token">
+						<xs:pattern value="[0-9]{1,50}"/>
 						<xs:maxLength value="50"/>
 					</xs:restriction>
 				</xs:simpleType>
@@ -329,6 +330,7 @@ Datum				Version				Autor
 				</xs:annotation>
 				<xs:simpleType>
 					<xs:restriction base="xs:token">
+						<xs:pattern value="[0-9]{1,50}"/>
 						<xs:maxLength value="50"/>
 					</xs:restriction>
 				</xs:simpleType>