Flocking a filedescriptor in a shell script

I thought this would give me uninterrupted begin-end pairs, but it doesn't: #!/bin/bash fun()( flock 1 || { echo >&2 "$BASHPID: FAIL: $?"; exit 1; } echo "$BASHPID begin" sleep 1; echo "$BASHPID end" ) fun & fun & fun & fun & fun & fun & fun & fun & fun & wait What am I doing wrong?