diff --git a/src/libstore/legacy-ssh-store.cc b/src/libstore/legacy-ssh-store.cc
index 855a7c99a..dfefdb9bc 100644
--- a/src/libstore/legacy-ssh-store.cc
+++ b/src/libstore/legacy-ssh-store.cc
@@ -105,6 +105,13 @@ struct LegacySSHStore : public Store
             readLongLong(conn->from); // download size
             info->narSize = readLongLong(conn->from);
 
+            if (GET_PROTOCOL_MINOR(conn->remoteVersion) >= 4) {
+                auto s = readString(conn->from);
+                info->narHash = s.empty() ? Hash() : Hash(s);
+                conn->from >> info->ca;
+                info->sigs = readStrings<StringSet>(conn->from);
+            }
+
             auto s = readString(conn->from);
             assert(s == "");
 
diff --git a/src/libstore/serve-protocol.hh b/src/libstore/serve-protocol.hh
index f8cc9a4b6..f67d1e258 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 0x203
+#define SERVE_PROTOCOL_VERSION 0x204
 #define GET_PROTOCOL_MAJOR(x) ((x) & 0xff00)
 #define GET_PROTOCOL_MINOR(x) ((x) & 0x00ff)
 
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 1668fdb2d..85bcbc22e 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -858,6 +858,8 @@ static void opServe(Strings opFlags, Strings opArgs)
                         // !!! Maybe we want compression?
                         out << info->narSize // downloadSize
                             << info->narSize;
+                        if (GET_PROTOCOL_MINOR(clientVersion) >= 4)
+                            out << (info->narHash ? info->narHash.to_string() : "") << info->ca << info->sigs;
                     } catch (InvalidPath &) {
                     }
                 }