timezones are lost sometimes, when using bind_rows

[pchtsp]

I'm pretty sure this started happening since I recently updated dplyr.
I use as.POSIXct to transform characters into datetime objects. It automatically assigns the timezone for the current timezone of the PC (in my case "Europe/Paris"). In some cases I enforce the timezone (with the argument tz=Sys.timezone()). In my pc, this last function returns "Europe/Paris".

Apparently, there is an issue when binding rows with two dataframes, where one has been manually assigned a timezone and the other has an automatic one, although I've checked they both show CET as timezone. Not sure if this is the only issue I had with dates.

The first case shows "2016-01-01 UTC" "2016-01-01 UTC". The rest show correctly "2016-01-01 01:00:00 CET" "2016-01-01 01:00:00 CET"
If I enforce both or I enforce non, it works ok.
If I try with rbindlist or rbind, the first case works ok.

library(dplyr)
library(magrittr)
library(data.table)

bind_rows(
  data.frame(a= 4, b= as.POSIXct("2016-01-01 01:00", tz= Sys.timezone()))
  ,data.frame(a= 4, b= as.POSIXct("2016-01-01 01:00"))
  ) %>% use_series(b)

bind_rows(
  data.frame(a= 4, b= as.POSIXct("2016-01-01 01:00", tz= Sys.timezone()))
  ,data.frame(a= 4, b= as.POSIXct("2016-01-01 01:00", tz= Sys.timezone()))
) %>% use_series(b)

bind_rows(
  data.frame(a= 4, b= as.POSIXct("2016-01-01 01:00"))
  ,data.frame(a= 4, b= as.POSIXct("2016-01-01 01:00"))
) %>% use_series(b)

rbindlist(list(
  data.frame(a= 4, b= as.POSIXct("2016-01-01 01:00", tz= Sys.timezone()))
  ,data.frame(a= 4, b= as.POSIXct("2016-01-01 01:00"))
)) %>% use_series(b)

rbind(
  data.frame(a= 4, b= as.POSIXct("2016-01-01 01:00", tz= Sys.timezone()))
  ,data.frame(a= 4, b= as.POSIXct("2016-01-01 01:00"))
) %>% use_series(b)

More info:

R version 3.3.1 (2016-06-21)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows >= 8 x64 (build 9200)

locale:
[1] LC_COLLATE=Spanish_Spain.1252  LC_CTYPE=Spanish_Spain.1252   
[3] LC_MONETARY=Spanish_Spain.1252 LC_NUMERIC=C                  
[5] LC_TIME=Spanish_Spain.1252    

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

other attached packages:
[1] data.table_1.10.0 magrittr_1.5      dplyr_0.5.0      

loaded via a namespace (and not attached):
[1] R6_2.1.2        assertthat_0.1  rsconnect_0.4.3 DBI_0.5-1       tools_3.3.1    
[6] tibble_1.1      Rcpp_0.12.5  

[krlmlr]

Thanks, confirmed.