Loop XPath is empty!

I made a transformation with only one "Get XML Data" step configured as follow:
- read xml from a file;
- loopxpath set up to /test
- defined a set of fields.

Running from Spoon this transformation works returning no errors, no warnings, only the expected result.
However, when I tried to run the same ktr from a java application I obtained the following error:

ERROR (version 6.1.0.1-196) : Loop XPath is empty!

but it is not true! I have already verified in the ktr file that the tag <loopxpath> has /test as value.

Any advice?
Thanks in advanced.