The last four dates of Aerosmith’s Aero-Vederci tour have been cancelled due to singer Steven Tyler’s “unexpected medical issues.” A prepared statement says Tyler’s expected to be “back on his feet soon, rocking the world.”

Tyler said in the same statement, “I need to deal with this right away, and get some rest and medical care immediately in order to sustain and maintain my future performances.”

The specific cause of the issues was not disclosed.