diff --git a/lix/libstore/remote-store.cc b/lix/libstore/remote-store.cc
index c36a3f130..808d3b6ac 100644
--- a/lix/libstore/remote-store.cc
+++ b/lix/libstore/remote-store.cc
@@ -265,10 +265,14 @@ kj::Promise<Result<std::shared_ptr<const ValidPathInfo>>>
 RemoteStore::queryPathInfoUncached(const StorePath & path)
 try {
     auto conn(TRY_AWAIT(getConnection()));
+    std::optional<UnkeyedValidPathInfo> pathInfo;
     try {
-        auto valid =
-            TRY_AWAIT(conn.sendCommand<bool>(WorkerProto::Op::QueryPathInfo, printStorePath(path)));
-        if (!valid) co_return result::success(nullptr);
+        pathInfo = TRY_AWAIT(conn.sendCommand<std::optional<UnkeyedValidPathInfo>>(
+            WorkerProto::Op::QueryPathInfo, printStorePath(path)
+        ));
+        if (!pathInfo) {
+            co_return result::success(nullptr);
+        }
     } catch (Error & e) {
         // Ugly backwards compatibility hack. TODO(fj#325): remove.
         if (e.msg().find("is not valid") != std::string::npos)
@@ -276,9 +280,7 @@ try {
         throw;
     }
 
-    co_return std::make_shared<ValidPathInfo>(
-        StorePath{path},
-        WorkerProto::Serialise<UnkeyedValidPathInfo>::read(*conn));
+    co_return std::make_shared<ValidPathInfo>(StorePath{path}, std::move(*pathInfo));
 } catch (...) {
     co_return result::current_exception();
 }
@@ -288,9 +290,9 @@ kj::Promise<Result<void>> RemoteStore::queryReferrers(const StorePath & path,
     StorePathSet & referrers)
 try {
     auto conn(TRY_AWAIT(getConnection()));
-    TRY_AWAIT(conn.sendCommand(WorkerProto::Op::QueryReferrers, printStorePath(path)));
-    for (auto & i : WorkerProto::Serialise<StorePathSet>::read(*conn))
-        referrers.insert(i);
+    referrers.merge(TRY_AWAIT(
+        conn.sendCommand<StorePathSet>(WorkerProto::Op::QueryReferrers, printStorePath(path))
+    ));
     co_return result::success();
 } catch (...) {
     co_return result::current_exception();
diff --git a/lix/libstore/worker-protocol.cc b/lix/libstore/worker-protocol.cc
index d91384c2e..bbe5af805 100644
--- a/lix/libstore/worker-protocol.cc
+++ b/lix/libstore/worker-protocol.cc
@@ -6,6 +6,7 @@
 #include "lix/libstore/worker-protocol-impl.hh"
 #include "lix/libutil/archive.hh"
 #include "lix/libstore/path-info.hh"
+#include <optional>
 
 namespace nix {
 
@@ -152,6 +153,27 @@ WireFormatGenerator WorkerProto::Serialise<UnkeyedValidPathInfo>::write(WriteCon
     co_yield renderContentAddress(pathInfo.ca);
 }
 
+std::optional<UnkeyedValidPathInfo>
+WorkerProto::Serialise<std::optional<UnkeyedValidPathInfo>>::read(ReadConn conn)
+{
+    bool valid;
+    conn.from >> valid;
+    if (valid) {
+        return WorkerProto::Serialise<UnkeyedValidPathInfo>::read(conn);
+    } else {
+        return std::nullopt;
+    }
+}
+
+WireFormatGenerator WorkerProto::Serialise<std::optional<UnkeyedValidPathInfo>>::write(
+    WriteConn conn, const std::optional<UnkeyedValidPathInfo> & pathInfo
+)
+{
+    co_yield pathInfo.has_value();
+    if (pathInfo.has_value()) {
+        co_yield WorkerProto::write(conn, *pathInfo);
+    }
+}
 
 SubstitutablePathInfo WorkerProto::Serialise<SubstitutablePathInfo>::read(ReadConn conn)
 {
diff --git a/lix/libstore/worker-protocol.hh b/lix/libstore/worker-protocol.hh
index 8b7624feb..84e17e54e 100644
--- a/lix/libstore/worker-protocol.hh
+++ b/lix/libstore/worker-protocol.hh
@@ -239,6 +239,8 @@ DECLARE_WORKER_SERIALISER(UnkeyedValidPathInfo);
 template<>
 DECLARE_WORKER_SERIALISER(std::optional<TrustedFlag>);
 template<>
+DECLARE_WORKER_SERIALISER(std::optional<UnkeyedValidPathInfo>);
+template<>
 DECLARE_WORKER_SERIALISER(SubstitutablePathInfo);
 
 template<typename T>