diff --git a/day01/.envrc b/day01/.envrc
new file mode 100644
index 0000000000000000000000000000000000000000..3550a30f2de389e537ee40ca5e64a77dc185c79b
--- /dev/null
+++ b/day01/.envrc
@@ -0,0 +1 @@
+use flake
diff --git a/day01/flake.nix b/day01/flake.nix
index 70189f0356a98da5c89c7e72a40b9ab6ff0edd88..716ad807a558336c198fbb28f3091a1a45316859 100644
--- a/day01/flake.nix
+++ b/day01/flake.nix
@@ -22,8 +22,7 @@
         defaultPackage = naerskBuildPackage { };
 
         devShell = with pkgs; mkShell {
-          buildInputs = buildInputs ++ [ cargo rustc rustfmt ];
-          RUST_SRC_PATH = rustPlatform.rustLibSrc;
+          buildInputs = [ cargo rustc rustfmt ];
         };
       });
 }