If the schema includes itself or through the another schema, Idea highlights the errors on some elements, as not defined in this schema. Example: <xs:element name="userrole"> <xs:complexType mixed="true"> <xs:sequence minOccurs="0"> <xs:any namespace="http://www.w3.org/1999/xhtml ##targetNamespace" minOccurs="0" maxOccurs="unbounded"></xs:any> </xs:sequence> </xs:complexType> </xs:element> <xs:element name="label"> <xs:complexType> <xs:attribute name="key" use="required"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:whiteSpace value="collapse"/> </xs:restriction> </xs:simpleType> </xs:attribute> </xs:complexType </xs:element> It's impossible to use the "label" element inside of the "userrole" element though it's defined by the schema. Oxygen XML Editor and Xalan XML Parser accepts this combination as valid, so I except the IntelliJ will do the same. Can you release a quick fix for us, please? It's critical for our projet. We have to use now the external tools to edit our xml files.