diff --git a/flake.nix b/flake.nix
index 67cc7a3..3ecfe68 100644
--- a/flake.nix
+++ b/flake.nix
@@ -2,8 +2,8 @@
   description = "Finite Difference Time Domain simulation binaries";
   inputs = {
     nixpkgs.url = "nixpkgs/nixos-22.05";
-    flake-utils.url = github:numtide/flake-utils;
-    rust-overlay.url = github:oxalica/rust-overlay;
+    flake-utils.url = "github:numtide/flake-utils";
+    rust-overlay.url = "github:oxalica/rust-overlay/45140fa526b1cb85498f717e355c79a54367cb1d";  #< TODO: unpin (pinned now to simplify nixpkgs updating)
   };
 
   outputs = { self, nixpkgs, flake-utils, rust-overlay }: