European Central Bank President Mario Draghi told a European lawmaker that the composition of the institution’s asset-purchase program can be changed if needed.

“While there is no reason to change the composition of the purchases at the moment, the program is sufficiently flexible to be adjusted should circumstances change,” Draghi said in a letter to Ramon Tremosa i Balcells published on the ECB’s website. “The implementation of the expanded asset purchase program is proceeding smoothly” and “concerns about the scarcity of bonds are therefore not warranted at this juncture,” he said.