diff --git a/Makefile b/Makefile
index e823a77..b9d24e1 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
 .POSIX:
-.PHONY: default build switch diff update install clean
+.PHONY: default build switch diff update fmt install clean
 
 default: diff switch
 
@@ -17,6 +17,9 @@ switch:
 update:
 	nix flake update
 
+fmt:
+	nix run nixpkgs#nixfmt-tree
+
 install:
 	# This consumes significant memory on the live USB because dependencies are
 	# downloaded to tmpfs. The configuration must be small, or the machine must