1 hour layover isn't enough at Beijing Capital Airport, right?

United from IAD to PEK
1hr layover
Air China from PEK to SIN

I just reviewed our itinerary and realized that we may not have enough time between flights. I booked the trip through Expedia as the full itinerary, but now it's looking like they messed up and didn't give us enough time to go through customs/immigration. I'm assuming you have to go through C/I upon arrival to PEK no matter what?
I'm seeing that my incoming United flight and outgoing Air China flights are both situated in T3. Hoping that means we're good?