DIO0 GPIO15 boot fail

Hi, i have an issue, the gateway works perfectly fine but i have a small problem, i have the gpio15 pulled down to ground with a 10k resistor, but if i connect the 1n4148 diode for dio0 on gpio15 the esp12e will not boot. If i leave the diode disconnected, power up the board and only then connect the diode on gpio15 it works like a charm, any idea about the reason ?

Thanks a lot