error "sm-open-connection" "Could not open network socket"

I tried to build sawfish from source on a CentOS system , but when I launch it (vnc based server) I get:

$ sawfish --no-rc

Lisp backtrace:
#3   sm-connect ...
#2   sm-init ...
#1   run-byte-code ...

error--> (error "sm-open-connection" "Could not open network socket")


This is on a CentOS 7.6 system:
$ cat /etc/redhat-release
CentOS Linux release 7.6.1810 (Core)

Using a recent clone:
$ sawfish --version
sawfish version 1.12.90


These are the SHA1's of the repos:
sawfish.git
93f35ecf6a870cbe595ad4d6831de84c3bf9ed01
rep-gtk.git
c66467cd7d9f2466458bd24191766aaa7a4b2042
librep.git
bf5d0487e2f796299a058610cbdf2ae91dd7b88f

Running a different VM like stumpwm works fine in the same environment.

Any ideas how to resolve this?

Thanks!
Best regards
//Petter

-- 
Sawfish ML