Hello,

I have a configuration similar to this:

  (service ntp-service-type
           (ntp-configuration
            (servers '("10.1.1.1" "10.2.2.2"))))

When running `guix system reconfigure`, I get this error:

Backtrace:
In srfi/srfi-1.scm:
   592:29 19 (map1 (#<<service> type: #<service-type nscd 7f9e976…> …))
   592:29 18 (map1 (#<<service> type: #<service-type guix 7f9e976…> …))
   592:29 17 (map1 (#<<service> type: #<service-type urandom-seed…> …))
   592:29 16 (map1 (#<<service> type: #<service-type syslog 7f9e9…> …))
   592:29 15 (map1 (#<<service> type: #<service-type static-netwo…> …))
   592:29 14 (map1 (#<<service> type: #<service-type mingetty 7f9…> …))
   592:29 13 (map1 (#<<service> type: #<service-type mingetty 7f9…> …))
   592:29 12 (map1 (#<<service> type: #<service-type mingetty 7f9…> …))
   592:29 11 (map1 (#<<service> type: #<service-type mingetty 7f9…> …))
   592:29 10 (map1 (#<<service> type: #<service-type mingetty 7f9…> …))
   592:29  9 (map1 (#<<service> type: #<service-type mingetty 7f9…> …))
   592:29  8 (map1 (#<<service> type: #<service-type agetty 7f9e9…> …))
   592:29  7 (map1 (#<<service> type: #<service-type console-font…> …))
   592:29  6 (map1 (#<<service> type: #<service-type virtual-term…> …))
   592:29  5 (map1 (#<<service> type: #<service-type openssh 7f9e…> …))
   592:29  4 (map1 (#<<service> type: #<service-type mysql 7f9e97…> …))
   592:17  3 (map1 (#<<service> type: #<service-type ntp 7f9e9764…> …))
In gnu/services/networking.scm:
   393:37  2 (ntp-shepherd-service _)
In srfi/srfi-1.scm:
   592:17  1 (map1 ("10.1.1.1" "10.2.2.2"))
In gnu/services/networking.scm:
    340:2  0 (ntp-server->string _)

gnu/services/networking.scm:340:2: In procedure ntp-server->string:
Throw to key `match-error' with args `("match" "no matching pattern" "10.1.1.1")'.

This is on commit e5efdbce21a0afcbb3e73cc7b59111ccf62cb532.