diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index bdd6891ac2f8..44f3845b45af 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -430,7 +430,8 @@ Path RemoteStore::addTextToStore(const string & name, const string & s,
 
     openConnection();
     writeInt(wopAddTextToStore, to);
-    writeString(userName, to);
+    if (GET_PROTOCOL_MINOR(daemonVersion) >= 15)
+        writeString(userName, to);
     writeString(name, to);
     writeString(s, to);
     writeStrings(references, to);
diff --git a/src/libstore/worker-protocol.hh b/src/libstore/worker-protocol.hh
index c7d3a726ab4c..7561d511a805 100644
--- a/src/libstore/worker-protocol.hh
+++ b/src/libstore/worker-protocol.hh
@@ -6,7 +6,7 @@ namespace nix {
 #define WORKER_MAGIC_1 0x6e697863
 #define WORKER_MAGIC_2 0x6478696f
 
-#define PROTOCOL_VERSION 0x10e
+#define PROTOCOL_VERSION 0x10f
 #define GET_PROTOCOL_MAJOR(x) ((x) & 0xff00)
 #define GET_PROTOCOL_MINOR(x) ((x) & 0x00ff)
 
diff --git a/src/nix-daemon/nix-daemon.cc b/src/nix-daemon/nix-daemon.cc
index 01f0c3ccb67a..68e76b464c66 100644
--- a/src/nix-daemon/nix-daemon.cc
+++ b/src/nix-daemon/nix-daemon.cc
@@ -284,7 +284,9 @@ static void performOp(bool trusted, unsigned int clientVersion,
     }
 
     case wopAddTextToStore: {
-        string userName = readString(from);
+        string userName = publicUserName();
+        if (GET_PROTOCOL_MINOR(clientVersion) >= 15)
+            userName = readString(from);
         string suffix = readString(from);
         string s = readString(from);
         PathSet refs = readStorePaths<PathSet>(from);