diff --git a/plugins/lsp/language-servers/default.nix b/plugins/lsp/language-servers/default.nix
index cc51058b..c42c6a95 100644
--- a/plugins/lsp/language-servers/default.nix
+++ b/plugins/lsp/language-servers/default.nix
@@ -186,10 +186,7 @@ let
     else if lib.hasAttr name lspPackages.customCmd then
       { inherit (lspPackages.customCmd.${name}) package cmd; }
     else
-      assert lib.assertMsg (lib.elem name lspPackages.unpackaged) "LSP server ${name} is unknown";
-      {
-        package = null;
-      };
+      { package = null; };
 
   generatedServers = lib.pipe ../../../generated/lspconfig-servers.json [
     lib.importJSON
diff --git a/tests/generated.nix b/tests/generated.nix
index 3f4eaff7..ed4d388e 100644
--- a/tests/generated.nix
+++ b/tests/generated.nix
@@ -39,6 +39,25 @@ let
   # The test fails if this is non-empty.
   errors = lib.concatStringsSep "\n" (
     checkDeclarations (
+      let
+        inherit (import ../plugins/lsp/lsp-packages.nix) unpackaged packages customCmd;
+      in
+      {
+        name = "lsp";
+        declarationFile = "plugins/lsp/lsp-packages.nix";
+
+        packages = builtins.attrValues packages;
+
+        declared = unpackaged ++ lib.attrsets.attrNames (packages // customCmd);
+
+        generated = lib.pipe ../generated/lspconfig-servers.json [
+          lib.importJSON
+          (builtins.map (lib.getAttr "name"))
+          lib.lists.unique
+        ];
+      }
+    )
+    ++ checkDeclarations (
       let
         inherit (import ../plugins/by-name/none-ls/packages.nix lib) noPackage packaged;
       in