How to update a field based on hierarchical picklist based child LOV

Parent field is set with some value "ABC" from LOV type Test1 in workflow

Now, when i try to update another field using expression

LookupValue("Test2",[&Parentfield])

I get below error

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Siebel

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[1] Error updating business component at step 'Siebel Operation 0'.(SBL-BPR-00187)

[2] This error is returned when the workflow/task is executing the Siebel Operation business service.(SBL-BPR-00100)

[3] No field matches identifier 'Parent Type'.

Please ask your systems administrator to check your application configuration.(SBL-DAT-00416)

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OK  

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