XML Signature Reference digest uses parent namespace

I need to sign an XML-File in Java, which needs to contain 3 References.

While 2 of them are valid (expected digest == actual digest), one is invalid.

The relevant part of the XML Looks like:

<QualifyingProperties xmlns="http://ift.tt/1kBwwA9" Target="Signature1">
    <SignedProperties Id="SignedProperties_1">
        <SignedSignatureProperties>
            <SigningTime>2014-11-27T13:49:36</SigningTime>
        </SignedSignatureProperties>
    </SignedProperties>
</QualifyingProperties>

The Reference only references the Element "SignedProperties" and its children.

As you can see the "QualifyingProperties" Element defines a namespace (xmlns="http://ift.tt/1kBwwA9") and i guess thats the problem:

After having a look at the log i found, that the "Pre-Digest" Value looks like:

<SignedProperties xmlns="http://ift.tt/1kBwwA9" Id="SignedProperties_1">
    <SignedSignatureProperties>
        <SigningTime>2014-11-27T13:49:36</SigningTime>
    </SignedSignatureProperties>
</SignedProperties>

While the "SignedProperties" Element in the real file does not contain the namespace, but its parent does.

I found out, that the actual digest matches the SHA-256 of the "Pre-Digest" value, while the expected digest matches the SHA-256 of the real file (without the namespace).

The Reference is created with the following code:

Reference sigPropRef = fac.newReference("#SignedProperties_1", fac.newDigestMethod(DigestMethod.SHA256, null),
    Collections.singletonList(sigPropTransform), "http://ift.tt/1e3V3K0", "reference-signedpropeties"
);

Where the sigPropTransform is a CanonicalizationMethod.EXCLUSIVE Transform.

My question is, how can i solve the problem, i.e. how can i prevent the namespace to be added to the "SignedProperties" Element, before calculating the digest?

If you need any other informations please leave a comment, i am pretty new to this theme, so i am not sure which informations are relevant and which not.

Thanks a lot!