diff --git a/tests/lsp-servers.nix b/tests/lsp-servers.nix
index d0675eb1..df857864 100644
--- a/tests/lsp-servers.nix
+++ b/tests/lsp-servers.nix
@@ -42,6 +42,12 @@ let
           # See https://github.com/neovim/nvim-lspconfig/blob/master/lua/lspconfig.lua
           "ruff_lsp"
           "bufls"
+          # Package ‘dotnet-core-combined’ is marked as insecure, refusing to evaluate.
+          # Dotnet SDK 6.0.428 is EOL, please use 8.0 (LTS) or 9.0 (Current)
+          # https://github.com/NixOS/nixpkgs/pull/358533
+          "dafny"
+          "fsautocomplete"
+          "omnisharp"
         ]
         ++ lib.optionals pkgs.stdenv.isDarwin [
           "fsautocomplete"
diff --git a/tests/test-sources/plugins/lsp/omnisharp.nix b/tests/test-sources/plugins/lsp/omnisharp.nix
index 7e8e9880..738d2d2d 100644
--- a/tests/test-sources/plugins/lsp/omnisharp.nix
+++ b/tests/test-sources/plugins/lsp/omnisharp.nix
@@ -4,7 +4,10 @@
       enable = true;
 
       servers.omnisharp = {
-        enable = true;
+        # Package ‘dotnet-core-combined’ is marked as insecure, refusing to evaluate.
+        # Dotnet SDK 6.0.428 is EOL, please use 8.0 (LTS) or 9.0 (Current)
+        # https://github.com/NixOS/nixpkgs/pull/358533
+        enable = false;
 
         settings = {
           enableEditorConfigSupport = true;