diff --git a/schema/cpacs_schema.xsd b/schema/cpacs_schema.xsd
index 77e63ae..dbe8790 100644
--- a/schema/cpacs_schema.xsd
+++ b/schema/cpacs_schema.xsd
@@ -12336,17 +12336,7 @@ cpacs@dlr.de
                     <xsd:element name="structure" minOccurs="0" type="ductStructureType"/>
                 </xsd:all>
                 <xsd:attribute name="uID" use="required" type="xsd:ID"/>
-                <xsd:attribute name="symmetry">
-                    <xsd:simpleType>
-                        <xsd:restriction base="xsd:string">
-                            <xsd:enumeration value="none"/>
-                            <xsd:enumeration value="inherit"/>
-                            <xsd:enumeration value="x-y-plane"/>
-                            <xsd:enumeration value="x-z-plane"/>
-                            <xsd:enumeration value="y-z-plane"/>
-                        </xsd:restriction>
-                    </xsd:simpleType>
-                </xsd:attribute>
+                <xsd:attribute name="symmetry" type="symmetryXyXzYzType"/>
             </xsd:extension>
         </xsd:complexContent>
     </xsd:complexType>