Only seen on ARMv7 and goes away when you comment out [this line](https://github.com/iojs/io.js/blob/013527ad1c6a1e8f94965b55c0f33dcdab0492d5/test/simple/test-timers-unref.js#L61) (which does `t.unref.bind(t)`). ``` node: ../src/async-wrap-inl.h:245: v8::Handle<v8::Value> node::AsyncWrap::MakeCallback(uint32_t, int, v8::Handle<v8::Value>*): Assertion `cb->IsFunction()' failed. ``` https://jenkins-node-forward.nodesource.com/job/iojs+v0.12+multi/nodes=node-forward-nodesource-armv7-ubuntu1404/13/console Could this be a libuv thing perhaps? ARMv7 machine now hooked up to the CI cluster and will run with the rest of them.