Adding Column of NA to a Grouped Table Crashes R

[DarioS]

The example is :

library(dplyr)
dataset <- data_frame(A = 1:10, B = 10:1, group = factor(sample(LETTERS[25:26], 10, TRUE)))
dataset %>% group_by(group) %>% mutate(prediction = factor(NA))

It results in :

*** caught segfault ***
address 0xfffffffffffffffc, cause 'memory not mapped'

If the table is not grouped, then there is no R crash.

The R session is :

R version 3.2.3 (2015-12-10)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 15.10

other attached packages:
[1] dplyr_0.4.3.9000