Singer Rihanna performs at Staples Center on April 8, 2013 in Los Angeles

Singer Rihanna performs at Staples Center on April 8, 2013 in Los Angeles

*Rihanna has missed another show on her Diamonds World Tour, this time passing up Monday night’s Houston performance due to an unidentified illness.

The pop star canceled a show last month in Boston, just the second city on the tour. A follow-up performance was also canned in Baltimore. On both occasions, the singer missed due to laryngitis.

Promoters Live Nation have “postponed” — and not canceled — the Houston date. “Unfortunately, as a result of illness Rihanna is unable to perform this evening at Houston’s Toyota Center. Fans are instructed to retain their tickets to this event pending rescheduled show date information,” the Live Nation statement reads.

The Diamonds tour is due to move on to the American Airlines Centre in Dallas on Tuesday night. At time of publication, the Dallas show was still listed as going ahead, reports Billboard.

Rihanna explained her latest ailment with a message on Instagram. “I was sick since San Diego! I kept working because I thought two days off after the Vegas show would be enough time to recover and I f**ked up, those were two days off from hell and today is not different! I’m sad and disappointed about it! I had all kinds of plans for Houston!” she wrote.

In other Rihanna news, Vogue has apparently put an end to speculation that the singer was the new face of Chanel. The magazine writes that Rihanna hasn’t yet revealed her partner in a “top secret ad campaign” but noted “it’s definitely not Chanel.”