diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index a98cadc80..05d499d1f 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -1199,7 +1199,7 @@ static void prim_path(EvalState & state, const Pos & pos, Value * * args, Value
     string name;
     Value * filterFun = nullptr;
     auto method = FileIngestionMethod::Recursive;
-    Hash expectedHash(htSHA256);
+    std::optional<Hash> expectedHash;
 
     for (auto & attr : *args[0]->attrs) {
         const string & n(attr.name);