Does the Ranger’s Companion add proficiency bonus to its save DCs?

@monstermanual @mikemearlsDoes an animal companion add the Ranger’s proficiency bonus to its save DCs (for example, a Mastiff’s bite)? The ranger’s proficiency bonus isn’t added to the beast’s save DCs, but a DM could certainly override that.

— Jeremy Crawford (@JeremyECrawford) September 3, 2014