diff --git a/pkgs/development/tools/millet/default.nix b/pkgs/development/tools/millet/default.nix
index e5100aeaee6e..ab22e97c5bcd 100644
--- a/pkgs/development/tools/millet/default.nix
+++ b/pkgs/development/tools/millet/default.nix
@@ -2,19 +2,25 @@
 
 rustPlatform.buildRustPackage rec {
   pname = "millet";
-  version = "0.3.8";
+  version = "0.3.9";
 
   src = fetchFromGitHub {
     owner = "azdavis";
     repo = pname;
     rev = "v${version}";
-    sha256 = "sha256-RTOFwgs9A7ESWT8g5EcVzmv9UGON/+cNj21VC8bURlk=";
+    sha256 = "sha256-mG8vpcBcFACfVa8IFuax81pDeiloi0ustbAy6MOYpZs=";
   };
 
-  cargoSha256 = "sha256-/yUyvFTaoQQ4Ttlp1IHye9Iu7iD2W/yhuHKC3Seu6k0=";
+  cargoSha256 = "sha256-QoD5c2QZRKRO0gV+buvJN6d2RgfkA65AHibwJ4Kg/q8=";
+
+  postPatch = ''
+    rm .cargo/config.toml
+  '';
 
   cargoBuildFlags = [ "--package" "lang-srv" ];
 
+  cargoTestFlags = [ "--package" "lang-srv" ];
+
   meta = with lib; {
     description = "A language server for Standard ML";
     homepage = "https://github.com/azdavis/millet";