diff --git a/src/hydra-queue-runner/nar-extractor.cc b/src/hydra-queue-runner/nar-extractor.cc
index 31c0db65..7619b2ee 100644
--- a/src/hydra-queue-runner/nar-extractor.cc
+++ b/src/hydra-queue-runner/nar-extractor.cc
@@ -11,29 +11,28 @@ struct Extractor : NARParseVisitor
 {
     class MyFileHandle : public FileHandle
     {
-        NarMemberData * memberData;
+        NarMemberData & memberData;
         uint64_t expectedSize;
         std::unique_ptr<HashSink> hashSink;
 
         public:
-            MyFileHandle(NarMemberData * memberData, uint64_t size) : memberData(memberData)
+            MyFileHandle(NarMemberData & memberData, uint64_t size) : memberData(memberData), expectedSize(size)
             {
-                expectedSize = size;
                 hashSink = std::make_unique<HashSink>(HashType::SHA256);
             }
 
             void receiveContents(std::string_view data) override
             {
-                *memberData->fileSize += data.size();
+                *memberData.fileSize += data.size();
                 (*hashSink)(data);
-                if (memberData->contents) {
-                    memberData->contents->append(data);
+                if (memberData.contents) {
+                    memberData.contents->append(data);
                 }
-                assert(memberData->fileSize <= expectedSize);
-                if (memberData->fileSize == expectedSize) {
+                assert(memberData.fileSize <= expectedSize);
+                if (memberData.fileSize == expectedSize) {
                     auto [hash, len] = hashSink->finish();
-                    assert(memberData->fileSize == len);
-                    memberData->sha256 = hash;
+                    assert(memberData.fileSize == len);
+                    memberData.sha256 = hash;
                     hashSink.reset();
                 }
             }
@@ -65,7 +64,7 @@ struct Extractor : NARParseVisitor
             .contents = filesToKeep.count(path) ? std::optional("") : std::nullopt,
         }).first->second;
 
-        return std::unique_ptr<MyFileHandle>(new MyFileHandle{memberData, size});
+        return std::make_unique<MyFileHandle>(*memberData, size);
     }
 
     void createSymlink(const Path & path, const std::string & target) override