diff --git a/lix/libstore/daemon.cc b/lix/libstore/daemon.cc
index 8362aca7c..c32857e9d 100644
--- a/lix/libstore/daemon.cc
+++ b/lix/libstore/daemon.cc
@@ -682,13 +682,7 @@ static void performOp(AsyncIoRoot & aio, TunnelLogger * logger, ref<Store> store
         logger->startWork();
         aio.blockOn(store->querySubstitutablePathInfos(pathsMap, infos));
         logger->stopWork();
-        to << infos.size();
-        for (auto & i : infos) {
-            to << store->printStorePath(i.first)
-               << (i.second.deriver ? store->printStorePath(*i.second.deriver) : "");
-            to << WorkerProto::write(*store, wconn, i.second.references);
-            to << i.second.downloadSize << i.second.narSize;
-        }
+        to << WorkerProto::write(*store, wconn, infos);
         break;
     }
 
diff --git a/lix/libstore/path-info.hh b/lix/libstore/path-info.hh
index ad022e752..9fc76027b 100644
--- a/lix/libstore/path-info.hh
+++ b/lix/libstore/path-info.hh
@@ -27,6 +27,9 @@ struct SubstitutablePathInfo
      * 0 = unknown
      */
     uint64_t narSize;
+
+    bool operator==(const SubstitutablePathInfo &) const = default;
+    bool operator!=(const SubstitutablePathInfo &) const = default;
 };
 
 using SubstitutablePathInfos = std::map<StorePath, SubstitutablePathInfo>;
diff --git a/lix/libstore/remote-store.cc b/lix/libstore/remote-store.cc
index 930cbd7a0..365729226 100644
--- a/lix/libstore/remote-store.cc
+++ b/lix/libstore/remote-store.cc
@@ -23,6 +23,7 @@
 #include "lix/libutil/thread-name.hh"
 #include "lix/libutil/thread-pool.hh"
 #include "lix/libutil/types.hh"
+#include "path-info.hh"
 
 #include <kj/async.h>
 #include <optional>
@@ -240,17 +241,7 @@ try {
     conn->to << WorkerProto::Op::QuerySubstitutablePathInfos;
     conn->to << WorkerProto::write(*this, *conn, pathsMap);
     conn.processStderr();
-    size_t count = readNum<size_t>(conn->from);
-    for (size_t n = 0; n < count; n++) {
-        SubstitutablePathInfo & info(infos[parseStorePath(readString(conn->from))]);
-        auto deriver = readString(conn->from);
-        if (deriver != "")
-            info.deriver = parseStorePath(deriver);
-        info.references = WorkerProto::Serialise<StorePathSet>::read(*this, *conn);
-        info.downloadSize = readLongLong(conn->from);
-        info.narSize = readLongLong(conn->from);
-    }
-
+    infos = WorkerProto::Serialise<SubstitutablePathInfos>::read(*this, *conn);
     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 d2226eb39..71adfe6f8 100644
--- a/lix/libstore/worker-protocol.cc
+++ b/lix/libstore/worker-protocol.cc
@@ -152,4 +152,25 @@ WireFormatGenerator WorkerProto::Serialise<UnkeyedValidPathInfo>::write(const St
     co_yield renderContentAddress(pathInfo.ca);
 }
 
+
+SubstitutablePathInfo WorkerProto::Serialise<SubstitutablePathInfo>::read(const Store & store, ReadConn conn)
+{
+    SubstitutablePathInfo info;
+    auto deriver = readString(conn.from);
+    if (deriver != "")
+        info.deriver = store.parseStorePath(deriver);
+    info.references = WorkerProto::Serialise<StorePathSet>::read(store, conn);
+    info.downloadSize = readLongLong(conn.from);
+    info.narSize = readLongLong(conn.from);
+    return info;
+}
+
+WireFormatGenerator WorkerProto::Serialise<SubstitutablePathInfo>::write(const Store & store, WriteConn conn, const SubstitutablePathInfo & info)
+{
+    co_yield (info.deriver ? store.printStorePath(*info.deriver) : "");
+    co_yield WorkerProto::write(store, conn, info.references);
+    co_yield info.downloadSize;
+    co_yield info.narSize;
+}
+
 }
diff --git a/lix/libstore/worker-protocol.hh b/lix/libstore/worker-protocol.hh
index 1c6c12aed..968082523 100644
--- a/lix/libstore/worker-protocol.hh
+++ b/lix/libstore/worker-protocol.hh
@@ -2,6 +2,7 @@
 ///@file
 
 #include "lix/libstore/common-protocol.hh"
+#include "path-info.hh"
 
 namespace nix {
 
@@ -230,6 +231,8 @@ template<>
 DECLARE_WORKER_SERIALISER(UnkeyedValidPathInfo);
 template<>
 DECLARE_WORKER_SERIALISER(std::optional<TrustedFlag>);
+template<>
+DECLARE_WORKER_SERIALISER(SubstitutablePathInfo);
 
 template<typename T>
 DECLARE_WORKER_SERIALISER(std::vector<T>);
diff --git a/tests/unit/libstore/data/libstore/worker-protocol/substitutable-path-infos.bin b/tests/unit/libstore/data/libstore/worker-protocol/substitutable-path-infos.bin
new file mode 100644
index 000000000..658f17dad
Binary files /dev/null and b/tests/unit/libstore/data/libstore/worker-protocol/substitutable-path-infos.bin differ
diff --git a/tests/unit/libstore/worker-protocol.cc b/tests/unit/libstore/worker-protocol.cc
index 0bc32ce69..e4c7ef500 100644
--- a/tests/unit/libstore/worker-protocol.cc
+++ b/tests/unit/libstore/worker-protocol.cc
@@ -3,6 +3,7 @@
 #include <gtest/gtest.h>
 
 #include "lix/libstore/worker-protocol.hh"
+#include "lix/libstore/path-info.hh"
 #include "lix/libstore/worker-protocol-impl.hh"
 #include "lix/libstore/derived-path.hh"
 #include "lix/libstore/build-result.hh"
@@ -283,4 +284,36 @@ VERSIONED_CHARACTERIZATION_TEST(
         },
     }))
 
+VERSIONED_CHARACTERIZATION_TEST(
+    WorkerProtoTest,
+    substitutablePathInfos,
+    "substitutable-path-infos",
+    defaultVersion,
+    (SubstitutablePathInfos{
+        {StorePath{
+             "g1w7hyyyy1w7hy3qg1w7hy3qgqqqqy3q-foo",
+         },
+         SubstitutablePathInfo{
+             std::nullopt,
+             {},
+             123456789,
+             987654321,
+         }},
+        {StorePath{
+             "g1w7hyyyy1w7hy3qg1w7hy3qgqqqqy3q-bar",
+         },
+         SubstitutablePathInfo{
+             StorePath{
+                 "g1w7hyyyy1w7hy3qg1w7hy3qgqqqqy3q-fox",
+             },
+             {
+                 StorePath{
+                     "g1w7hyyyy1w7hy3qg1w7hy3qgqqqqy3q-other",
+                 },
+             },
+             987654321,
+             123456789,
+         }},
+    })
+)
 }