diff --git a/src/libstore/binary-cache-store.cc b/src/libstore/binary-cache-store.cc
index 848669ae8..b5a47c6ce 100644
--- a/src/libstore/binary-cache-store.cc
+++ b/src/libstore/binary-cache-store.cc
@@ -147,7 +147,7 @@ ref<const ValidPathInfo> BinaryCacheStore::addToStoreCommon(
        write the compressed NAR to disk), into a HashSink (to get the
        NAR hash), and into a NarAccessor (to get the NAR listing). */
     HashSink fileHashSink{HashAlgorithm::SHA256};
-    std::shared_ptr<SourceAccessor> narAccessor;
+    std::shared_ptr<NarAccessor> narAccessor;
     HashSink narHashSink{HashAlgorithm::SHA256};
     {
         FdSink fileSink(fdTemp.get());
@@ -205,7 +205,7 @@ ref<const ValidPathInfo> BinaryCacheStore::addToStoreCommon(
     if (config.writeNARListing) {
         nlohmann::json j = {
             {"version", 1},
-            {"root", listNarDeep(*narAccessor, CanonPath::root)},
+            {"root", narAccessor->getListing()},
         };
 
         upsertFile(std::string(info.path.hashPart()) + ".ls", j.dump(), "application/json");
diff --git a/src/libstore/remote-fs-accessor.cc b/src/libstore/remote-fs-accessor.cc
index 2f768871a..7297723e1 100644
--- a/src/libstore/remote-fs-accessor.cc
+++ b/src/libstore/remote-fs-accessor.cc
@@ -84,7 +84,7 @@ std::shared_ptr<SourceAccessor> RemoteFSAccessor::accessObject(const StorePath &
         auto narAccessor = makeNarAccessor(std::move(nar));
 
         try {
-            nlohmann::json j = listNarDeep(*narAccessor, CanonPath::root);
+            nlohmann::json j = narAccessor->getListing();
             writeFile(listingFile, j.dump());
         } catch (...) {
             ignoreExceptionExceptInterrupt();
diff --git a/src/libutil/include/nix/util/nar-accessor.hh b/src/libutil/include/nix/util/nar-accessor.hh
index 388dc1440..fa20497a8 100644
--- a/src/libutil/include/nix/util/nar-accessor.hh
+++ b/src/libutil/include/nix/util/nar-accessor.hh
@@ -10,13 +10,24 @@ namespace nix {
 
 struct Source;
 
+/**
+ * A SourceAccessor for NAR files that provides access to the listing structure.
+ */
+struct NarAccessor : SourceAccessor
+{
+    /**
+     * Get the NAR listing structure.
+     */
+    virtual const NarListing & getListing() const = 0;
+};
+
 /**
  * Return an object that provides access to the contents of a NAR
  * file.
  */
-ref<SourceAccessor> makeNarAccessor(std::string && nar);
+ref<NarAccessor> makeNarAccessor(std::string && nar);
 
-ref<SourceAccessor> makeNarAccessor(Source & source);
+ref<NarAccessor> makeNarAccessor(Source & source);
 
 /**
  * Create a NAR accessor from a NAR listing (in the format produced by
@@ -33,12 +44,12 @@ GetNarBytes seekableGetNarBytes(const std::filesystem::path & path);
 
 GetNarBytes seekableGetNarBytes(Descriptor fd);
 
-ref<SourceAccessor> makeLazyNarAccessor(NarListing listing, GetNarBytes getNarBytes);
+ref<NarAccessor> makeLazyNarAccessor(NarListing listing, GetNarBytes getNarBytes);
 
 /**
  * Creates a NAR accessor from a given stream and a GetNarBytes getter.
  * @param source Consumed eagerly. References to it are not persisted in the resulting SourceAccessor.
  */
-ref<SourceAccessor> makeLazyNarAccessor(Source & source, GetNarBytes getNarBytes);
+ref<NarAccessor> makeLazyNarAccessor(Source & source, GetNarBytes getNarBytes);
 
 } // namespace nix
diff --git a/src/libutil/nar-accessor.cc b/src/libutil/nar-accessor.cc
index a31c67ab2..10b222f73 100644
--- a/src/libutil/nar-accessor.cc
+++ b/src/libutil/nar-accessor.cc
@@ -4,13 +4,18 @@
 
 namespace nix {
 
-struct NarAccessor : public SourceAccessor
+struct NarAccessorImpl : NarAccessor
 {
     NarListing root;
 
     GetNarBytes getNarBytes;
 
-    NarAccessor(std::string && nar)
+    const NarListing & getListing() const override
+    {
+        return root;
+    }
+
+    NarAccessorImpl(std::string && nar)
         : root{[&nar]() {
             StringSource source(nar);
             return parseNarListing(source);
@@ -20,18 +25,18 @@ struct NarAccessor : public SourceAccessor
     {
     }
 
-    NarAccessor(Source & source)
+    NarAccessorImpl(Source & source)
         : root{parseNarListing(source)}
     {
     }
 
-    NarAccessor(Source & source, GetNarBytes getNarBytes)
+    NarAccessorImpl(Source & source, GetNarBytes getNarBytes)
         : root{parseNarListing(source)}
         , getNarBytes{std::move(getNarBytes)}
     {
     }
 
-    NarAccessor(NarListing && listing, GetNarBytes getNarBytes)
+    NarAccessorImpl(NarListing && listing, GetNarBytes getNarBytes)
         : root{std::move(listing)}
         , getNarBytes{std::move(getNarBytes)}
     {
@@ -127,24 +132,24 @@ struct NarAccessor : public SourceAccessor
     }
 };
 
-ref<SourceAccessor> makeNarAccessor(std::string && nar)
+ref<NarAccessor> makeNarAccessor(std::string && nar)
 {
-    return make_ref<NarAccessor>(std::move(nar));
+    return make_ref<NarAccessorImpl>(std::move(nar));
 }
 
-ref<SourceAccessor> makeNarAccessor(Source & source)
+ref<NarAccessor> makeNarAccessor(Source & source)
 {
-    return make_ref<NarAccessor>(source);
+    return make_ref<NarAccessorImpl>(source);
 }
 
-ref<SourceAccessor> makeLazyNarAccessor(NarListing listing, GetNarBytes getNarBytes)
+ref<NarAccessor> makeLazyNarAccessor(NarListing listing, GetNarBytes getNarBytes)
 {
-    return make_ref<NarAccessor>(std::move(listing), getNarBytes);
+    return make_ref<NarAccessorImpl>(std::move(listing), getNarBytes);
 }
 
-ref<SourceAccessor> makeLazyNarAccessor(Source & source, GetNarBytes getNarBytes)
+ref<NarAccessor> makeLazyNarAccessor(Source & source, GetNarBytes getNarBytes)
 {
-    return make_ref<NarAccessor>(source, getNarBytes);
+    return make_ref<NarAccessorImpl>(source, getNarBytes);
 }
 
 GetNarBytes seekableGetNarBytes(const std::filesystem::path & path)