ggplotly() bar chart render issue

ggplotly() renders a layered bar chart incorrectly; results in stacked bars, see the figures. Any way to remedy? Thanks, Kimmo

data_before = data.frame(
       year = c(2014,2014,2014,2015,2015,2015,2016,2016,2016),
       pet = c("dog","cat","bird","dog","cat","bird","dog","cat","bird"),
       wt = c(56, 25, 26, 10, 19, 41, 16, 17, 13)
  )

data_after = data.frame(
  year = c(2014,2014,2014,2015,2015,2015,2016,2016,2016),
  pet = c("dog","cat","bird","dog","cat","bird","dog","cat","bird"),
  wt = c(49, 18, 19,  3, 12, 34,  9, 10,  6)
)

ggplot()+
  geom_bar(data=data_before,aes(year,wt,fill=pet),stat="identity",position="dodge",width = 0.9,alpha=0.5)+
  geom_bar(data=data_after,aes(year,wt,fill=pet),stat="identity",position="dodge",width = 0.9)+
  xlab("Year") +
  ylab("Weight")

ggplotly()

ggplot chart (correct):

ggplotly() render (incorrect)

Start by running the supplied R reproduction and compare the ggplot and ggplotly figures, focusing on the two layered geom_bar calls using position="dodge". Trace how this chart is converted and rendered, then verify that the ggplotly result preserves the separate dodged bars and transparency shown by the source chart.