niv add niv: url_template not found

[nmattia]

~/niv$ niv add niv

Reading sources file
One or more packages failed to update:
niv: Update failed: Key could not be found: url_template
CallStack (from HasCallStack):
  error, called at src/Niv/Update.hs:79:25 in niv-0.1.1-JA4AHhZ4RkBKIGCn3c0RWr:Niv.Update