diff --git a/src/hydra-queue-runner/build-remote.cc b/src/hydra-queue-runner/build-remote.cc
index a82a95e6..8f8d6532 100644
--- a/src/hydra-queue-runner/build-remote.cc
+++ b/src/hydra-queue-runner/build-remote.cc
@@ -107,27 +107,27 @@ static void openConnection(Machine::ptr machine, Path tmpDir, int stderrFD, Chil
 }
 
 
-static void copyClosureTo(std::timed_mutex & sendMutex, Store & destStore,
-    FdSource & from, FdSink & to, const StorePathSet & paths,
+static void copyClosureTo(
+    Machine::Connection & conn,
+    Store & destStore,
+    const StorePathSet & paths,
     bool useSubstitutes = false)
 {
     StorePathSet closure;
     destStore.computeFSClosure(paths, closure);
 
-    WorkerProto::WriteConn wconn { .to = to };
-    WorkerProto::ReadConn rconn { .from = from };
     /* Send the "query valid paths" command with the "lock" option
        enabled. This prevents a race where the remote host
        garbage-collect paths that are already there. Optionally, ask
        the remote host to substitute missing paths. */
     // FIXME: substitute output pollutes our build log
-    to << ServeProto::Command::QueryValidPaths << 1 << useSubstitutes;
-    WorkerProto::write(destStore, wconn, closure);
-    to.flush();
+    conn.to << ServeProto::Command::QueryValidPaths << 1 << useSubstitutes;
+    WorkerProto::write(destStore, conn, closure);
+    conn.to.flush();
 
     /* Get back the set of paths that are already valid on the remote
        host. */
-    auto present = WorkerProto::Serialise<StorePathSet>::read(destStore, rconn);
+    auto present = WorkerProto::Serialise<StorePathSet>::read(destStore, conn);
 
     if (present.size() == closure.size()) return;
 
@@ -139,14 +139,14 @@ static void copyClosureTo(std::timed_mutex & sendMutex, Store & destStore,
 
     printMsg(lvlDebug, "sending %d missing paths", missing.size());
 
-    std::unique_lock<std::timed_mutex> sendLock(sendMutex,
+    std::unique_lock<std::timed_mutex> sendLock(conn.machine->state->sendLock,
         std::chrono::seconds(600));
 
-    to << ServeProto::Command::ImportPaths;
-    destStore.exportPaths(missing, to);
-    to.flush();
+    conn.to << ServeProto::Command::ImportPaths;
+    destStore.exportPaths(missing, conn.to);
+    conn.to.flush();
 
-    if (readInt(from) != 1)
+    if (readInt(conn.from) != 1)
         throw Error("remote machine failed to import closure");
 }
 
@@ -257,7 +257,7 @@ BasicDerivation sendInputs(
             destStore.computeFSClosure(basicDrv.inputSrcs, closure);
             copyPaths(destStore, localStore, closure, NoRepair, NoCheckSigs, NoSubstitute);
         } else {
-            copyClosureTo(conn.machine->state->sendLock, destStore, conn.from, conn.to, basicDrv.inputSrcs, true);
+            copyClosureTo(conn, destStore, basicDrv.inputSrcs, true);
         }
 
         auto now2 = std::chrono::steady_clock::now();