await not working in release build with react-native@0.50.1

await is working in the debug build but not in the release build. This happens with react-native@0.50.1 but not with react-native@0.48.4. It happens on device and on simulators. I see the first log but not the second:

console.log('before await')
const value = await AsyncStorage.getItem(key)
console.log('after await value: ' + value)

I tried with different build settings for dead code stripping, bitcode and performance optimization, but it didn't help.

What can be the reason? Maybe something with babel? Or do I have to adapt the code to use "then"?

AsyncStorage.getItem(key).then(...

Thanks!