XSD: Element with namespace is not expected

I have a simple XSD Schema:

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns="urn:myNamespace" xmlns:xs="http://ift.tt/tphNwY" xmlns:ds="http://ift.tt/uq6naF" elementFormDefault="qualified" attributeFormDefault="unqualified" id="myList">
    <xs:import namespace="http://ift.tt/uq6naF" schemaLocation="http://ift.tt/1pH7diL"/>
    <xs:element name="abc">
      <xs:complexType>
        <xs:sequence>
                <xs:element name="testElement" />
                <xs:element name="Signature" type="ds:SignatureType"/>
            </xs:sequence>
        </xs:complexType>
    </xs:element>
</xs:schema>

and XML file, which I want to validate:

<?xml version="1.0" encoding="UTF-8"?>
<abc>
    <testElement>
    </testElement>
    <Signature xmlns="http://ift.tt/uq6naF">
        <SignedInfo>
            <CanonicalizationMethod Algorithm="http://ift.tt/y9fQ1c"/>
            <SignatureMethod Algorithm="http://ift.tt/zf1Wx4"/>
            <Reference URI="">
                <Transforms>
                    <Transform Algorithm="http://ift.tt/A1C4L2"/>
                </Transforms>
                <DigestMethod Algorithm="http://ift.tt/yuvO4a"/>
                <DigestValue>value1</DigestValue>
            </Reference>
        </SignedInfo>
        <SignatureValue>value2</SignatureValue>
        <KeyInfo><KeyName/></KeyInfo>
    </Signature>
</abc>

I use xmllint and I'm getting the following error:

file.xml:5: element Signature: Schemas validity error : Element '{http://ift.tt/KrD3Sf': This element is not expected. Expected is ( Signature ).
file.xml fails to validate

What am I doing wrong with XML namespaces? Is the problem in XSD or in XML?