Periodic current spikes on sleep

[kammutierspule]

I'm measuring the current of the following code:

int main( void )
{
 while( 1 )
 {
 __SEV();
 __WFE();
 __WFE();
 }
}

I'm not using softdevices.

I have nothing more connected to the board than the power.

I measure about 0.320 uA which is good, I think... but I got periodic 100uA current spikes every 70ms which gives the average of 0.861 uA

Is it expected?