diff --git a/home/common.nix b/home/common.nix
index 6f9c9c7..f65ceff 100644
--- a/home/common.nix
+++ b/home/common.nix
@@ -3,6 +3,7 @@
   inputs,
   config,
   system,
+  lib,
   ...
 }:
 {
@@ -48,6 +49,11 @@
       init.defaultBranch = "mainline";
       diff.tool = "vimdiff";
       merge.tool = "vimdiff";
+      # provide `git mergetool -t nixfmt`
+      mergetool.nixfmt = {
+        cmd = "${lib.getExe pkgs.nixfmt-rfc-style} --mergetool \"$BASE\" \"$LOCAL\" \"$REMOTE\" \"$MERGED\"";
+        trustExitCode = true;
+      };
       core.excludesfile = toString (
         pkgs.writeText ".gitignore_global" ''
           # Direnv stuff #