Help, i broke my nix channel

error:
… while evaluating the attribute ‘config’
at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:1:12284:
… while calling the ‘seq’ builtin
at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:1:12293:
(stack trace truncated; use ‘–show-trace’ to show the full, detailed trace)

   error: syntax error, unexpected '=', expecting ';'
   at /etc/nixos/configuration.nix:121:29:
      120|   # Change binaryCaches mirror
      121|   nix.settings.substituters = "https://mirrors.tuna.tsinghua.edu.cn/nix-channels/store"
         |                             ^
      122|