Samsung has positioned its Bixby digital assistant as the crowning jewel of the upcoming Galaxy S8 smartphone. As it turns out, however, there’s one pretty significant flaw that has emerged: the fact that Bixby’s headlining feature – voice control – won’t be available when the Galaxy S8 goes on sale April 21.

The South Korean electronics giant in a statement to The Verge on Tuesday said Bixby’s voice control feature wouldn’t be available on its flagship in the US until later this spring. The spokesperson didn’t specify the reason for the delay.

Other Bixby features including Vision, Home and Reminder, Samsung confirmed, would be available on all models when the Galaxy S8 launches globally next week.

The Wall Street Journal, citing people familiar with the matter, notes that during internal tests in recent weeks, the performance of Bixby’s voice recognition in English has lagged behind that of the Korean version. As such, executives haven’t yet decided exactly when to make Bixby available in English. One source said the rollout could be pushed back until as late as the end of May.

To say that Bixby is an important part of the Galaxy S8 would be an understatement. Aside from the smartphone’s bezel-less display, the digital assistant is probably the top feature – it has its own dedicated button on the device, after all.