diff --git a/Makefile b/Makefile
index b3d57978..0fe29473 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,6 @@
-.PHONY: all all-tests test
-NIX_PATH := nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixpkgs-unstable.tar.gz
+.PHONY: all all-tests test format
+NIXPKGS_REV := nixpkgs-unstable
+NIX_PATH := nixpkgs=https://github.com/NixOS/nixpkgs/archive/${NIXPKGS_REV}.tar.gz
 
 all: all-tests
 
@@ -11,3 +12,6 @@ ifndef TEST
 	$(error Use 'make test TEST=<test_name>' to run desired test)
 endif
 	nix-shell --pure tests -I ${NIX_PATH} -A run.${TEST}
+
+format:
+	./format