Based on MAGIC observations from 2007 June to July, we have obtained an integral upper limit to the VHE energy emission of the globular cluster M13 of F (E > 200 GeV) < 5.1 x 10(-12) cm(-2) s(-1), and differential upper limits for E > 140 GeV. Those limits allow us to constrain the population of millisecond pulsars within M13 and to test models for acceleration of leptons inside their magnetospheres and surrounding. We conclude that in M13 either millisecond pulsars are fewer than expected or they accelerate leptons less efficiently than predicted.
