diff --git a/pkgs/build-support/trivial-builders/test/concat-test.nix b/pkgs/build-support/trivial-builders/test/concat-test.nix
index 5ce435619069..a893408854e5 100644
--- a/pkgs/build-support/trivial-builders/test/concat-test.nix
+++ b/pkgs/build-support/trivial-builders/test/concat-test.nix
@@ -2,7 +2,7 @@
 let
   stri = writeText "pathToTest";
   txt1 = stri "abc";
-  txt2 = stri hello;
+  txt2 = stri (builtins.toString hello);
   res = concatText "textToTest" [ txt1 txt2 ];
 in
 runCommand "test-concatPaths" { } ''