Error: No target! rel=_pobj and src=of

[Amen Belayneh]

Sentence: "Part of it is, of course."
Output:

Dependency relations:                           

Error: No target! rel=_pobj and src=of          
    _advmod(be, of_course)                      
    _subj(be, it)                               
    _quantity(it, part)                         
    _det(it, part)                              
    _advmod(part, of)                           

Attributes:                                     

    tense(be, present)                          
    subscript-TAG(be, .v)                       
    pos(be, verb)                               
    pos(., punctuation)                         
    pos(of, WORD)                               
    idiom-FLAG(of_course, T)                    
    pos(of_course, adv)                         
    pronoun-FLAG(it, T)                         
    gender(it, neuter)                          
    definite-FLAG(it, T)                        
    pos(it, noun)                               
    pos(of, prep)                               
    subscript-TAG(part, .i)                     
    pos(part, adj)                              
    pos(,, punctuation)                         

[Linas Vepštas]

still an issue.