diff --git a/src/nix-env/nix-env.cc b/src/nix-env/nix-env.cc
index 213a20d93..ab1d8f713 100644
--- a/src/nix-env/nix-env.cc
+++ b/src/nix-env/nix-env.cc
@@ -172,7 +172,7 @@ static void loadSourceExpr(EvalState & state, const SourcePath & path, Value & v
        directory). */
     else if (st.type == InputAccessor::tDirectory) {
         auto attrs = state.buildBindings(maxAttrs);
-        attrs.alloc("_combineChannels").mkList(0);
+        state.mkList(attrs.alloc("_combineChannels"), 0);
         StringSet seen;
         getAllExprs(state, path, seen, attrs);
         v.mkAttrs(attrs);