Set height of picker with react-native

I have a picker in my react-native ios app and want to set the height but the example won't honor flex, a style height or a height attribute.

<Picker
    style={[styles.testbox, {borderColor: '#00F', flex:1, height: 100}]}
    selectedValue={this.state.language}
    height={100}
    onValueChange={(itemValue, itemIndex) => this.setState({language: itemValue})}>
    <Picker.Item label="Java" value="java" />
    <Picker.Item label="JavaScript" value="js" />
</Picker>