Rangemode tozero only applies to positive values

I have a scatter chart that sometimes include only one data point and that point may have a negative value in one or both axis. For positive data, with rangemode set to tozero, the view appears as expected (i.e. the origin and the data point are both visible). However, for negative data, the axis auto scales to zero to plus one, meaning the actual data point is out of view.
If I add a false data point at the origin, set to mode: "none", the scaling behaves better, but now I have an unwanted entry in my legend.
Is there a solution that allows correct scaling without introducing a false series to the legend? (a false series that the user cannot detect is fine)