[Flutter]table-calender : Cant show markers Vertically

I am using Flutter table_calender package. I want the markers to be vertically placed. Tried using calenderBuilders but inside markerBuilder if I return Column it doesn't show any markers. Returning Row works just fine. Here is my code:

            calendarBuilders: CalendarBuilders(
                  markerBuilder: (BuildContext context, date, events) {
                    if (events.isEmpty) return SizedBox();
                    return Column(
                      mainAxisAlignment: MainAxisAlignment.start,
                      crossAxisAlignment: CrossAxisAlignment.center,
                      children: [
                        Container(
                          // height: 7,
                          width: 12,
                          decoration: BoxDecoration(
                              shape: BoxShape.circle, color: Colors.white),
                        ),
                      ],
                    );
                  },
                ),