Flush log for a specific app

What's going wrong?

When I run pm2 flush <app_id> or pm2 flush <app_name> pm2 do not flushed the specific logs but indicates that it has been done :

root@vps:/home/node# pm2 flush 2
[PM2] Logs flushed
root@vps:/home/node# pm2 flush appName
[PM2] Flushing:
[PM2] /var/www/dev/logs/out.log
[PM2] /var/www/dev/logs/error.log
[PM2] Logs flushed

If I run pm2 flush it works and clears all logs from all apps.

PM2 report

================================================
--- Daemon -------------------------------------------------
pm2d version         : 3.5.1
node version         : 8.10.0
node path            : not found
argv                 : /usr/bin/node,/usr/local/lib/node_modules/pm2/lib/Daemon.js
argv0                : node
user                 : root
uid                  : 0
gid                  : 0
uptime               : 76min
================================================
--- CLI ----------------------------------------------------
local pm2            : 3.5.1
node version         : 8.10.0
node path            : /usr/local/bin/pm2
argv                 : /usr/bin/node,/usr/local/bin/pm2,report
argv0                : node
user                 : root
uid                  : 0
gid                  : 0
================================================
--- System info --------------------------------------------
arch                 : x64
platform             : linux
type                 : Linux
cpus                 : Intel Core Processor (Haswell, no TSX)
cpus nb              : 2
freemem              : 6804459520
totalmem             : 8165056512
home                 : /root
================================================

Reproduce the reported behavior with pm2 flush 2, pm2 flush appName, and pm2 flush under the PM2 3.5.1 environment described in the report. Trace the CLI handling for app-specific and global flush commands; done means the targeted app logs are cleared without clearing unrelated app logs, while the global command still clears all logs.