(CNBC) — Starbucks cafes are facing mounting competition from other Starbucks locations and that’s going to hurt the stock, one Wall Street firm said Wednesday.

BMO Capital Markets downgraded Starbucks shares to market perform from outperform after its researched indicated that store overlap has grown to such an extreme point that they are hurting each other’s sales.

“Cannibalization likely has increased,” wrote BMO analyst Andrew Strelzik in the note. “Strong new store performance appears to be coming – at least in part – at the expense of existing store traffic.”

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