isOpen() misbehaviour

Hello,

From the doc, it says:

"isOpen returns a logical value, whether the connection is currently open."

But actually it seems to die on closed connections:

con <- file()
isOpen(con)

[1] TRUE

close(con)
isOpen(con)

Error in isOpen(con) : invalid connection

Is it expected ?
Tested on R-3.0.2 and R version 3.1.0 Patched (2014-06-11 r65921) on
linux x86_64

Karl