Prometheus graphs occasionally have incorrect Y scale

In some cases, the Y-axis on prometheus graphs appears to be too small to encompass the maximum Y-value of the data. For example:

This graph appears to scale from 0ms to about 10ms, but the point I'm hovering over shows a value of 25.11ms which is off the scale. The graph line is cut off.

/cc @jivanvl @joshlambert