Tooltips: "Tether is not defined"

Created by: lgkonline

Today I wanted to try the Bootstrap 4 alpha and when I want to use the tooltips plugin I get this error in my debugger console:

Uncaught ReferenceError: Tether is not defined
bootstrap.js:2967

show @ bootstrap.js:2967
_enter @ bootstrap.js:316
4n.extend.proxy.n.isFunction.e @ jquery-1.11.0.min.js:2
n.each.n.event.special.(anonymous function).handle @ jquery-1.11.0.min.js:3
n.event.dispatch @ jquery-1.11.0.min.js:3
n.event.add.r.handle @ jquery-1.11.0.min.js:3