diff --git a/slsReceiverSoftware/src/ClientInterface.cpp b/slsReceiverSoftware/src/ClientInterface.cpp
index 192daab98..09ee538bc 100644
--- a/slsReceiverSoftware/src/ClientInterface.cpp
+++ b/slsReceiverSoftware/src/ClientInterface.cpp
@@ -83,7 +83,8 @@ void ClientInterface::startTCPServer() {
         try {
             auto socket = server.accept();
             try {
-                verifyLock();
+                verifyLock(); // lock should be checked only for set (not get),
+                              // Move it back?
                 ret = decodeFunction(socket);
             } catch (const RuntimeError &e) {
                 // We had an error needs to be sent to client
@@ -1115,7 +1116,7 @@ int ClientInterface::set_additional_json_header(Interface &socket) {
             json[key] = value;
         }
     }
-    verifyIdle(socket);
+    // verifyIdle(socket); allowing it to be set on the fly
     LOG(logDEBUG1) << "Setting additional json header: " << sls::ToString(json);
     impl()->setAdditionalJsonHeader(json);
     return socket.Send(OK);
@@ -1531,7 +1532,7 @@ int ClientInterface::increment_file_index(Interface &socket) {
 int ClientInterface::set_additional_json_parameter(Interface &socket) {
     char args[2][SHORT_STR_LENGTH]{};
     socket.Receive(args);
-    verifyIdle(socket);
+    // verifyIdle(socket); allowing it to be set on the fly
     LOG(logDEBUG1) << "Setting additional json parameter (" << args[0]
                    << "): " << args[1];
     impl()->setAdditionalJsonParameter(args[0], args[1]);
diff --git a/slsReceiverSoftware/src/DataStreamer.cpp b/slsReceiverSoftware/src/DataStreamer.cpp
index 9c55803a7..5bb21895e 100644
--- a/slsReceiverSoftware/src/DataStreamer.cpp
+++ b/slsReceiverSoftware/src/DataStreamer.cpp
@@ -69,7 +69,9 @@ void DataStreamer::SetFlippedDataX(int fd) { flippedDataX = fd; }
 
 void DataStreamer::SetAdditionalJsonHeader(
     const std::map<std::string, std::string> &json) {
-    additionJsonHeader = json;
+    std::lock guard<std::mutex> guard(additionalJsonMutex);
+    additionalJsonHeader = json;
+    isAdditionalJsonUpdated = true;
 }
 
 void DataStreamer::CreateZmqSockets(int *nunits, uint32_t port,
@@ -232,7 +234,13 @@ int DataStreamer::SendHeader(sls_receiver_header *rheader, uint32_t size,
     zHeader.quad = *quadEnable;
     zHeader.completeImage =
         (header.packetNumber < generalData->packetsPerFrame ? false : true);
-    zHeader.addJsonHeader = additionJsonHeader;
+
+    if (isAdditionalJsonUpdated) {
+        std::lock_guard<std::mutex> guard(additionalalJsonMutex);
+        localAdditionalJsonHeader = additionalJsonHeader;
+        isAdditionalalJsonUpdated = false;
+    }
+    zHeader.addJsonHeader = localAdditionalJsonHeader;
 
     return zmqSocket->SendHeader(index, zHeader);
 }
diff --git a/slsReceiverSoftware/src/DataStreamer.h b/slsReceiverSoftware/src/DataStreamer.h
index bbfc5aba9..bfe9d69bd 100644
--- a/slsReceiverSoftware/src/DataStreamer.h
+++ b/slsReceiverSoftware/src/DataStreamer.h
@@ -166,7 +166,17 @@ class DataStreamer : private virtual slsDetectorDefs, public ThreadObject {
     int flippedDataX;
 
     /** additional json header */
-    std::map<std::string, std::string> additionJsonHeader;
+    std::map<std::string, std::string> additionalJsonHeader;
+
+    /** Used by streamer thread to update local copy (reduce number of locks
+     * during streaming) */
+    std::atomic<bool>{false};
+
+    /** mutex to update json and to read and update local copy */
+    std::mutex additionalJsonMutex;
+
+    /** local copy of additional json header  (it can be update on the fly) */
+    std::map<std::string, std::string> localAdditionalJsonHeader;
 
     /** Aquisition Started flag */
     bool startedFlag{nullptr};