"key values mismatch" error

Hey, I’m trying to run the letsencrypt client (as root, no params) on my Arch server with nginx and getting this error message:

Nginx Restart Failed!
2015/12/03 20:38:15 [emerg] 8124#0:
SSL_CTX_use_PrivateKey_file("/var/lib/letsencrypt/snakeoil/0001_key.pem") failed (SSL: error:0B080074:x509 certificate routines:X509_check_private_key:key values mismatch)

Lower down are generic “urn:acme:error:connection :: The server could not connect to the client for DV” errors, probably caused by this one.