--- a/rel/files/mongooseimctl
+++ b/rel/files/mongooseimctl
@@ -222,7 +222,7 @@
 	    CTL_LOCKFILE="$CONNLOCKDIR/$CTL_CONN"
 	    (
 		exec 8>"$CTL_LOCKFILE"
-		if flock --nb 8; then
+		if flock -n 8; then
 		    ctlexec $CTL_CONN "$@"
                     ssresult=$?
                     # segregate from possible flock exit(1)