diff --git a/rpc/rpc_impl.hh b/rpc/rpc_impl.hh
index d7ee5c4b34..a9926d1ade 100644
--- a/rpc/rpc_impl.hh
+++ b/rpc/rpc_impl.hh
@@ -149,18 +149,18 @@ public:
 class simple_output_stream {
     char* _p;
 public:
-    simple_output_stream(sstring& s) : _p(s.begin()) {}
+    simple_output_stream(sstring& s, size_t start) : _p(s.begin() + start) {}
     void write(const char* data, size_t size) {
         _p = std::copy_n(data, size, _p);
     }
 };
 
 template <typename Serializer, typename... T>
-inline sstring marshall(Serializer& serializer, const T&... args) {
+inline sstring marshall(Serializer& serializer, size_t head_space, const T&... args) {
     measuring_output_stream measure;
     do_marshall(serializer, measure, args...);
-    sstring ret(sstring::initialized_later(), measure.size());
-    simple_output_stream out(ret);
+    sstring ret(sstring::initialized_later(), measure.size() + head_space);
+    simple_output_stream out(ret, head_space);
     do_marshall(serializer, out, args...);
     return ret;
 }
@@ -285,19 +285,15 @@ auto send_helper(MsgType t, signature<Ret (InArgs...)> sig) {
         promise<> sent; // will be fulfilled when data is sent
         auto fsent = sent.get_future();
         dst.get_stats_internal().pending++;
-        sstring data = marshall(dst.serializer(), args...);
-        sstring header(sstring::initialized_later(), 24);
-        auto p = header.begin();
+        sstring data = marshall(dst.serializer(), 24, args...);
+        auto p = data.begin();
         *unaligned_cast<uint64_t*>(p) = net::hton(uint64_t(t));
         *unaligned_cast<int64_t*>(p + 8) = net::hton(msg_id);
-        *unaligned_cast<uint64_t*>(p + 16) = net::hton(data.size());
-        dst.out_ready() = do_with(std::move(header), std::move(data),
-                [&dst] (sstring& header, sstring& data) {
-            return dst.out_ready().then([&dst, &header, &data] () mutable {
-                return dst.out().write(header).then([&dst, &data] {
-                    return dst.out().write(data).then([&dst] {
-                        return dst.out().flush();
-                    });
+        *unaligned_cast<uint64_t*>(p + 16) = net::hton(data.size() - 24);
+        dst.out_ready() = do_with(std::move(data), [&dst] (sstring& data) {
+            return dst.out_ready().then([&dst, &data] () mutable {
+                return dst.out().write(data).then([&dst] {
+                    return dst.out().flush();
                 });
             });
         }).finally([&dst, sent = std::move(sent)] () mutable {
@@ -316,14 +312,12 @@ template <typename Serializer, typename MsgType>
 inline
 future<>
 protocol<Serializer, MsgType>::server::connection::respond(int64_t msg_id, sstring&& data) {
-    std::array<char, 16> header;
-    *unaligned_cast<int64_t*>(header.data()) = net::hton(msg_id);
-    *unaligned_cast<uint64_t*>(header.data() + 8) = net::hton(data.size());
-    return do_with(header, std::move(data), [this, msg_id] (auto& header, const sstring& data) {
-        return this->out().write(header.data(), header.size()).then([this, &data] {
-            return this->out().write(data.begin(), data.size()).then([this] {
-                return this->out().flush();
-            });
+    auto p = data.begin();
+    *unaligned_cast<int64_t*>(p) = net::hton(msg_id);
+    *unaligned_cast<uint64_t*>(p + 8) = net::hton(data.size() - 16);
+    return do_with(std::move(data), [this, msg_id] (const sstring& data) {
+        return this->out().write(data.begin(), data.size()).then([this] {
+            return this->out().flush();
         });
     });
 }
@@ -333,10 +327,10 @@ inline future<> reply(wait_type, future<RetTypes...>&& r, int64_t msgid, typenam
     try {
         auto&& data = r.get();
         auto str = ::apply(marshall<Serializer, const RetTypes&...>,
-                std::tuple_cat(std::make_tuple(std::ref(client.serializer())), std::move(data)));
+                std::tuple_cat(std::make_tuple(std::ref(client.serializer()), 16), std::move(data)));
         return client.respond(msgid, std::move(str));
     } catch (std::exception& ex) {
-        return client.respond(-msgid, ex.what());
+        return client.respond(-msgid, sstring(sstring::initialized_later(), 16) + ex.what());
     }
 }