mget doesn't find columns (without specifying the environment explicitly)

[ecoRoland]

DT <- data.table(a=1:2, b=c("x", "y")) 
DT[, get("a")] 
#[1] 1 2 
DT[, mget("a", inherits = TRUE)] 
#Error: value for ‘a’ not found

It works if the correct environment is specified:

DT[, mget("a", as.environment(.SD))] 
#   a
#1: 1
#2: 2

According to Arun:

The j-exp is parsed and checked for get(), but not mget(). Therefore the SD environment isn't constructed with the required columns.