line chart shows data from previous year upon drilldown

[isaacl]

When drilling down to a month where I only have data for part of the month I will see the rest of the month filled with the previous years data. For example my current data for went until DEC 21 2016 however when i drill down to Dec 2016 I will see a data line on my line chart for a specific product that I had in 2015 continue from the 21st till the end of the month. This extra line will disappear when I apply a data slicer and filter out 2015.