The Arabic Treebank (ATB), released by the Linguistic Data Consortium, contains multiple annotation files for each source file, due in part to the role of diacritic inclusion in the annotation process. The data is made available in both ”vocalized ” and ”unvocalized ” forms, with and without the diacritic marks, respectively. Much parsing work with the ATB has used the unvocalized form, on the basis that it more closely represents the ”real-world ” situation. We point out some problems with this usage of the unvocalized data and explain why the unvocalized form does not in fact represent ”real-world ” data. This is due to some aspects of the treebank annotation that to our knowledge have never before been published. 1.