diff --git a/flake.lock b/flake.lock
index 14fa168..cf4c1e9 100644
--- a/flake.lock
+++ b/flake.lock
@@ -58,11 +58,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1790689126,
-        "narHash": "sha256-ilerN1WLSvF+HMjziC/Wv99J5y02maDH+6hZPwsORKg=",
+        "lastModified": 1793341285,
+        "narHash": "sha256-Y1CiZ4SoBUjLQyQM/pY+rS2dXD3CHLPstF0lmOc73D4=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "b4fd65b198c599cbe814fcb9f42d25d021595ec9",
+        "rev": "1c89083e451e891152365b799595cf7790a43325",
         "type": "github"
       },
       "original": {
diff --git a/flake.nix b/flake.nix
index b774ad4..769b18b 100644
--- a/flake.nix
+++ b/flake.nix
@@ -167,7 +167,10 @@
                 pkgs.markdownlint-cli2
               ]
               ++ pkgs.lib.optionals pkgs.stdenv.isLinux [
-                pkgs.cargo-llvm-cov
+                # FIXME: drop once nixpkgs builds cargo-llvm-cov against the LLVM that
+                # rustc 1.99 emits profiles for; its test suite fails on the profraw
+                # version mismatch, but the tool works with the toolchain llvm-tools.
+                (pkgs.cargo-llvm-cov.overrideAttrs { doCheck = false; })
                 pkgs.perf
               ];