join two tbl_dt

[tempranillo1]

If I try to join two tbl_dt object (ie data.table objects) i have an error. The simplest reprodcible example is:

library(dplyr)
mtcars2 <- tbl_dt(mtcars) %>%
           mutate(name = rownames(mtcars))
a <- mtcars2 %>% select(mpg:wt, name)
b <- mtcars2 %>% select(qsec:name)
left_join(a, b, by = "name")

Error in left_join.data.table(a, b, by = "name") : 
  could not find function "copy"

Of course loading data.table package help, but I've created package where I import dplyr package and do not import data.table.

I thik replacing

x <- copy(x)
y <- copy(y)

to

x <- data.table::copy(x)
y <- data.table::copy(y)

in join-dt.r will be sufficient.

My sessionInfo() is

R version 3.1.1 (2014-07-10)
Platform: i386-w64-mingw32/i386 (32-bit)

locale:
[1] LC_COLLATE=Polish_Poland.1250  LC_CTYPE=Polish_Poland.1250    LC_MONETARY=Polish_Poland.1250 LC_NUMERIC=C                  
[5] LC_TIME=Polish_Poland.1250    

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

other attached packages:
[1] dplyr_0.3.0.2  roxygen2_4.0.2 devtools_1.6.1 sos_1.3-8      brew_1.0-6    

loaded via a namespace (and not attached):
 [1] assertthat_0.1   chron_2.3-45     data.table_1.9.4 DBI_0.3.1        lazyeval_0.1.9   magrittr_1.0.1   packrat_0.4.1-1  parallel_3.1.1  
 [9] plyr_1.8.1       Rcpp_0.11.3      reshape2_1.4     rstudioapi_0.1   stringr_0.6.2    tools_3.1.1