geom_point borders in ggplot2 2.0.0

Question

In the most recent verion of ggplot2, a change appears to have been made in the way that geom_point is rendered.

For instance, if I attempt to do alpha shading, then I get the following appearance:

library(ggplot2)

ggplot(mtcars) +
  geom_point(aes(wt, qsec),
            size  = 8,
            stroke = 0,
            alpha = .3)

How can I get ggplot to mimic its earlier behavior, and have the points appear without any border?

Edit:

As I said, this is occurring in:

the most recent version of ggplot2

> sessionInfo()
R version 3.2.3 (2015-12-10)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows >= 8 x64 (build 9200)

locale:
[1] LC_COLLATE=English_United States.1252  LC_CTYPE=English_United States.1252    LC_MONETARY=English_United States.1252 LC_NUMERIC=C                          
[5] LC_TIME=English_United States.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] ggplot2_2.0.0

loaded via a namespace (and not attached):
[1] labeling_0.3     colorspace_1.2-6 scales_0.3.0     plyr_1.8.3       tools_3.2.3      gtable_0.1.2     Rcpp_0.12.2      grid_3.2.3       munsell_0.4.2   

Edit 2:

These borders also occur in the github version: ggplot2_2.0.0.9000

Answer 1

In an email to the ggplot2 listserve, Hadley mentions "geom_point() now uses shape 19 instead of 16. This looks much better on the default Linux graphics device. (It’s very slightly smaller than the old point, but it shouldn’t affect any graphics significantly)."

library(ggplot2)
ggplot(mtcars) +
  geom_point(aes(wt, qsec),
             size  = 8,
             stroke = 0,
             shape=16,
             alpha = .3)