This paper presents arguments for a re-analysis of the b-prefix in Gulf Arabic dialects. Similar to several other dialects, Gulf Arabic possesses a b-prefix that is inserted before the p-stem (prefix form) of the verb. However, the Gulf Arabic b-prefix differs substantially from the one encountered in other Arabic dialects. According to most previous studies, the Gulf Arabic b-prefix encodes future tense or intentive mood or a combination of these. Based on a thorough survey of the use of this particle in modern speech, I suggest that it is used in Gulf Arabic today as a generalized marker of the irrealis mood rather than being limited to function as a future/intentive marker. Futurity is one - but not the only or necessarily the most important one - of its connotations. Meanwhile, another marker, rah, emerges as an obvious future marker in some parts of the dialectal area.