diff --git a/pkgs/lib/default.nix b/pkgs/lib/default.nix
index 3f7ba67ecf1e..ca8820034338 100644
--- a/pkgs/lib/default.nix
+++ b/pkgs/lib/default.nix
@@ -484,6 +484,7 @@ rec {
     else if all __isList list then concatLists list
     else if all __isAttrs list then mergeAttrs list
     else if all (x: true == x || false == x) list then fold logicalOR false list
+    else if all (x: x == toString x) list then concatStrings x
     else abort "${name}: Cannot merge values.";
 
   mergeTypedOption = typeName: predicate: merge: name: list: