Ambiguous column name 'CustID'.

Hello Experts,

I have 2 tables Customer and GiftCerticate both has a column name CustID

am trying to write the below query to check email and dob from Customer and this custid should exist
in giftcertificate table ...

SELECT CustID FROM Customer, GiftCertificate
WHERE Customer.CustEmail='test@test.com'  
AND Customer.CustDOB='15/10/1906'  
AND GiftCertificate.CustID = Customer.CustID


but i am getting this error
Ambiguous column name 'CustID'..

please can someone advise
thanks