Backtrace:
In ice-9/boot-9.scm:
  66: 19 [call-with-prompt prompt0 ...]
In ice-9/eval.scm:
 432: 18 [eval # #]
In ice-9/boot-9.scm:
2404: 17 [save-module-excursion #<procedure 2717900 at ice-9/boot-9.scm:4051:3 ()>]
4056: 16 [#<procedure 2717900 at ice-9/boot-9.scm:4051:3 ()>]
1727: 15 [%start-stack load-stack ...]
1732: 14 [#<procedure 272bb70 ()>]
In unknown file:
   ?: 13 [primitive-load "/gnu/store/hnbqdmfh1bwma8nmpai6ci76h5j6bl7j-guix-0.12.0-4.d9da/bin/.guix-real"]
In guix/ui.scm:
1228: 12 [run-guix-command system "reconfigure" "-n" "--no-grub" "/etc/config.scm"]
In ice-9/boot-9.scm:
 160: 11 [catch srfi-34 #<procedure 563ae00 at guix/ui.scm:432:2 ()> ...]
 160: 10 [catch system-error ...]
In guix/scripts/system.scm:
 954: 9 [#<procedure 56272a0 at guix/scripts/system.scm:946:2 ()>]
 841: 8 [process-action reconfigure ("/etc/config.scm") ...]
In guix/store.scm:
1249: 7 [run-with-store # ...]
In guix/scripts/system.scm:
 853: 6 [#<procedure 5896780 at guix/scripts/system.scm:845:8 (state)> #]
 611: 5 [perform-action reconfigure # # ...]
In gnu/system.scm:
 634: 4 [operating-system-derivation # # #f]
In gnu/services.scm:
 595: 3 [fold-services # # #]
 586: 2 [service-back-edges #]
In srfi/srfi-1.scm:
 465: 1 [fold #<procedure add-edges (service edges)> #<vlist ()> ...]
In gnu/services.scm:
 584: 0 [add-edges #<procedure 594b4a0 at /etc/config.scm:23:2 (state)> #<vlist ()>]

gnu/services.scm:584:50: In procedure add-edges:
gnu/services.scm:584:50: In procedure struct_vtable: Wrong type argument in position 1 (expecting struct): #<procedure 594b4a0 at /etc/config.scm:23:2 (state)>