1 files changed, 6 insertions, 0 deletions
diff --git a/lib/types.nix b/lib/types.nix
index 07a6cc69fdc..3c21e34879c 100644
--- a/lib/types.nix
+++ b/lib/types.nix
@@ -71,6 +71,12 @@ rec {
       merge = lib.concatStringsSep "\n";
     };
 
+    commas = mkOptionType {
+      name = "string";
+      check = builtins.isString;
+      merge = lib.concatStringsSep ",";
+    };
+
     envVar = mkOptionType {
       name = "environment variable";
       inherit (string) check;