diff --git a/nix/sources.json b/nix/sources.json
index 02da6e43e..e0170c0e8 100644
--- a/nix/sources.json
+++ b/nix/sources.json
@@ -5,10 +5,10 @@
         "homepage": null,
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "68e7dce0a6532e876980764167ad158174402c6f",
-        "sha256": "024vd8hqdakvhyzxw6zpm6awkxm9bx0xg5hmrpsfl16nnrwy3z34",
+        "rev": "a9b86fc2290b69375c5542b622088eb6eca2a7c3",
+        "sha256": "1mssfzy1nsansjmp5ckyl8vbk32va3abchpg19ljyak0xblxnjs1",
         "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/68e7dce0a6532e876980764167ad158174402c6f.tar.gz",
+        "url": "https://github.com/NixOS/nixpkgs/archive/a9b86fc2290b69375c5542b622088eb6eca2a7c3.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "rust-overlay": {
@@ -17,10 +17,10 @@
         "homepage": "",
         "owner": "oxalica",
         "repo": "rust-overlay",
-        "rev": "2ef910a6276a2f34513d18f2f826a8dea72c3b3f",
-        "sha256": "0pjgvqi1l0y2chzjs9lh6qvx962k71ny8c1c2rn6h4afxfpl52dv",
+        "rev": "ada8266712449c4c0e6ee6fcbc442b3c217c79e1",
+        "sha256": "1y5fq080nqknps35pmfdyxy7vys1bzdkqzrhh41fxq3jkiw74idg",
         "type": "tarball",
-        "url": "https://github.com/oxalica/rust-overlay/archive/2ef910a6276a2f34513d18f2f826a8dea72c3b3f.tar.gz",
+        "url": "https://github.com/oxalica/rust-overlay/archive/ada8266712449c4c0e6ee6fcbc442b3c217c79e1.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     }
 }
diff --git a/shell.nix b/shell.nix
index 6453a0140..14f0c1206 100644
--- a/shell.nix
+++ b/shell.nix
@@ -22,6 +22,7 @@ pkgs.mkShell {
     rustToolchain
 
     # Other
+    cargo-llvm-cov
     mdbook
     yamlfmt
     which # used by "cargo xtask fmt"