When I attempt a basic http post, I can see that the server is returning a normal 400. But the client seems to just crash with an error I can’t make sense of. I have the following code

static Future<TradApiServerResponse> submitPhone(
  String phone, String code) async {
    http.Response response = await http.post(
      Uri.parse("$urlbase/api/submitphone"),
      headers: <String, String>{
        'Content-Type': 'application/json; charset=UTF-8',
      },
      body: jsonEncode(<String, String>{
        'code': code,
        'phone': phone,
      }),
    );
    if (response.statusCode == 200) {

When stepping trough it never gets to the if statement. It just locks up then crashes. The server is responding. I can curl or use the browser directly and it works fine

Error
dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 329:10  createErrorWithStack
dart-sdk/lib/_internal/js_dev_runtime/patch/core_patch.dart 265:28            _throw
dart-sdk/lib/core/errors.dart 120:5                                           throwWithStackTrace
dart-sdk/lib/async/zone.dart 1386:11                                          callback
dart-sdk/lib/async/schedule_microtask.dart 40:11                              _microtaskLoop
dart-sdk/lib/async/schedule_microtask.dart 49:5                               _startMicrotaskLoop
dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 181:7            <fn>
Application finished.

How can I figure out what the problem is? Sorry I am new to flutter