Pound reverse proxy HTTPS pb

Hello,

I found and install Pound reverse Proxy on a Redhat linux 7.x.
I can't start in HTTPS mode.
The log file say : SSL_CTX_use_PrivateKey_file failed.

I create my own cerficate (poundcert.pem) + priv key (poundkey.pem)
[encrypted key] + poundkeyout.pem[unencrypted key] in the
/usr/local/etc/pound/ directory.

I configure pound.cfg (same directory):
ListenHTTPS machine,443 /usr/local/etc/pound/poundcert.pem

Where can I specified the location of the private unencrypted key file
?

I start the SSL engine with command :
openssl s_server -cert poundcrt.pem -key poundkeyout.pem.
It works. Any suggestions ?

Thanks

Greg