Unicode displayed as integers in tooltip when produced by ggplotly()

Hi, 

When using ggplotly to create the graph, the tooltip shows the information as integers. 
plot_ly working fine.

```r
library(ggplot2)
library(plotly)
p <- ggplot(cars)+
  geom_point(aes(1, 1, color = "اختبار"))
ggplotly(p)
```
Note: reprex encode unicode as ?????
Many thanks