marginLeft not a functioning property

[daredoes]

This block runs but throws an error
<CSSTransition defaultStyle={{ "margin-left": 0 }} enterStyle={{ "margin-left": transit(200, 250, "linear")}} leaveStyle={{ "margin-left": transit(0, 250, "linear")}} activeStyle={{ "margin-left": 200 }} active={this.state.showSider} >
This block throws no errors, but does not run.
<CSSTransition defaultStyle={{ marginLeft: 0 }} enterStyle={{ marginLeft: transit(200, 250, "linear")}} leaveStyle={{ marginLeft: transit(0, 250, "linear")}} activeStyle={{ marginLeft: 200 }} active={this.state.showSider} >

For some reason, marginLeft is not getting converted into margin-left before being inserted into the CSS.