diff --git a/src/libstore/legacy-ssh-store.cc b/src/libstore/legacy-ssh-store.cc
index f9b0b42c83d..ddfd17d641b 100644
--- a/src/libstore/legacy-ssh-store.cc
+++ b/src/libstore/legacy-ssh-store.cc
@@ -28,6 +28,7 @@ struct LegacySSHStore : public Store
         FdSink to;
         FdSource from;
         int remoteVersion;
+        bool good = true;
     };
 
     std::string host;
@@ -42,7 +43,7 @@ struct LegacySSHStore : public Store
         , connections(make_ref<Pool<Connection>>(
             std::max(1, (int) maxConnections),
             [this]() { return openConnection(); },
-            [](const ref<Connection> & r) { return true; }
+            [](const ref<Connection> & r) { return r->good; }
             ))
         , master(
             host,
@@ -58,7 +59,7 @@ struct LegacySSHStore : public Store
     {
         auto conn = make_ref<Connection>();
         conn->sshConn = master.startCommand(
-            fmt("%s --serve --write", remoteProgram)
+            fmt("command time %s --serve --write", remoteProgram)
             + (remoteStore.get() == "" ? "" : " --store " + shellEscape(remoteStore.get())));
         conn->to = FdSink(conn->sshConn->in.get());
         conn->from = FdSource(conn->sshConn->out.get());
@@ -130,18 +131,48 @@ struct LegacySSHStore : public Store
 
         auto conn(connections->get());
 
-        conn->to
-            << cmdImportPaths
-            << 1;
-        copyNAR(source, conn->to);
-        conn->to
-            << exportMagic
-            << info.path
-            << info.references
-            << info.deriver
-            << 0
-            << 0;
-        conn->to.flush();
+        if (GET_PROTOCOL_MINOR(conn->remoteVersion) >= 4) {
+
+            conn->to
+                << cmdAddToStoreNar
+                << info.path
+                << info.deriver
+                << info.narHash.to_string(Base16, false)
+                << info.references
+                << info.registrationTime
+                << info.narSize
+                << info.ultimate
+                << info.sigs
+                << info.ca;
+            try {
+                copyNAR(source, conn->to);
+            } catch (...) {
+                conn->good = false;
+                throw;
+            }
+            conn->to.flush();
+
+        } else {
+
+            conn->to
+                << cmdImportPaths
+                << 1;
+            try {
+                copyNAR(source, conn->to);
+            } catch (...) {
+                conn->good = false;
+                throw;
+            }
+            conn->to
+                << exportMagic
+                << info.path
+                << info.references
+                << info.deriver
+                << 0
+                << 0;
+            conn->to.flush();
+
+        }
 
         if (readInt(conn->from) != 1)
             throw Error("failed to add path '%s' to remote host '%s', info.path, host");
diff --git a/src/libstore/serve-protocol.hh b/src/libstore/serve-protocol.hh
index f67d1e2580a..9fae6d5349f 100644
--- a/src/libstore/serve-protocol.hh
+++ b/src/libstore/serve-protocol.hh
@@ -5,7 +5,7 @@ namespace nix {
 #define SERVE_MAGIC_1 0x390c9deb
 #define SERVE_MAGIC_2 0x5452eecb
 
-#define SERVE_PROTOCOL_VERSION 0x204
+#define SERVE_PROTOCOL_VERSION 0x205
 #define GET_PROTOCOL_MAJOR(x) ((x) & 0xff00)
 #define GET_PROTOCOL_MINOR(x) ((x) & 0x00ff)
 
@@ -18,6 +18,7 @@ typedef enum {
     cmdBuildPaths = 6,
     cmdQueryClosure = 7,
     cmdBuildDerivation = 8,
+    cmdAddToStoreNar = 9,
 } ServeCommand;
 
 }
diff --git a/src/nix-daemon/nix-daemon.cc b/src/nix-daemon/nix-daemon.cc
index a2e54b93c05..644fa6681de 100644
--- a/src/nix-daemon/nix-daemon.cc
+++ b/src/nix-daemon/nix-daemon.cc
@@ -707,6 +707,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
 
         logger->startWork();
 
+        // FIXME: race if addToStore doesn't read source?
         store.cast<Store>()->addToStore(info, *source, (RepairFlag) repair,
             dontCheckSigs ? NoCheckSigs : CheckSigs, nullptr);
 
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 942fe50e86c..fe68f681ae2 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -924,6 +924,28 @@ static void opServe(Strings opFlags, Strings opArgs)
                 break;
             }
 
+            case cmdAddToStoreNar: {
+                if (!writeAllowed) throw Error("importing paths is not allowed");
+
+                ValidPathInfo info;
+                info.path = readStorePath(*store, in);
+                in >> info.deriver;
+                if (!info.deriver.empty())
+                    store->assertStorePath(info.deriver);
+                info.narHash = Hash(readString(in), htSHA256);
+                info.references = readStorePaths<PathSet>(*store, in);
+                in >> info.registrationTime >> info.narSize >> info.ultimate;
+                info.sigs = readStrings<StringSet>(in);
+                in >> info.ca;
+
+                // FIXME: race if addToStore doesn't read source?
+                store->addToStore(info, in, NoRepair, NoCheckSigs);
+
+                out << 1; // indicate success
+
+                break;
+            }
+
             default:
                 throw Error(format("unknown serve command %1%") % cmd);
         }