diff --git a/pkgs/build-support/docker/default.nix b/pkgs/build-support/docker/default.nix
index 92e003c64afb..adb13a7f457a 100644
--- a/pkgs/build-support/docker/default.nix
+++ b/pkgs/build-support/docker/default.nix
@@ -592,7 +592,7 @@ rec {
     in
     runCommand "${baseNameOf name}.tar${compress.ext}" {
       inherit (stream) imageName;
-      passthru = {
+      passthru = stream.passthru // {
         inherit (stream) imageTag;
         inherit stream;
       };