Prince Philip is battling an illness. The 91-year-old royal was set to join wife Queen Elizabeth II at the Royal National Institute of Blind People gala event at St. James' Palace on Monday, May 3, but fell ill and had to miss the official engagement.

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"The Duke is unwell, but he will be at the service tomorrow," a Buckingham Palace rep tells Us Weekly. "Just a bit under the weather."

No further details on Philip's illness were released.

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Philip, who will celebrate his 92nd birthday on June 10, is still expected to attend Tuesday's Coronation Service at Westminster Abbey to mark the Queen's 60th anniversary.

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Princes William and Harry's grandfather has been in good health for the past year after being hospitalized in August 2012 with a bladder infection. He left the Aberdeen Royal Infirmary in Scotland after a five-night stay with a big smile on his face.

This article originally appeared on Prince Philip "Unwell," Cancels Gala Appearance