No brakes, booster/ vacuum line frozen?

[pec]

Hi,

Since its freezing outside, my brake pedal is hard and there is little to no brakes,
booster is not working. So i took a hairdryer and warmed up the vacuumline where it goes into the brakebooster (checkvalve). after that brakes were fine again.
then later it froze up again same problem.
is this vacuum line a loose part? it goes from the booster into the front wing.
its about 50 cm long. or is the booster fozen up (moist?)

'98 boxster 2.5 manual shift.

thank you

Pec.