diff --git a/lib/types.nix b/lib/types.nix
index ddd37f260c9a6..b602d1d7f781f 100644
--- a/lib/types.nix
+++ b/lib/types.nix
@@ -436,10 +436,7 @@ rec {
 
     # Deprecated; should not be used because it quietly concatenates
     # strings, which is usually not what you want.
-    string = separatedString "" // {
-      name = "string";
-      deprecationMessage = "See https://github.com/NixOS/nixpkgs/pull/66346 for better alternative types.";
-    };
+    string = throw "The type `types.string` is deprecated. See https://github.com/NixOS/nixpkgs/pull/66346 for better alternative types.";
 
     passwdEntry = entryType: addCheck entryType (str: !(hasInfix ":" str || hasInfix "\n" str)) // {
       name = "passwdEntry ${entryType.name}";