diff --git a/producer/api/cpp/src/request_handler_tcp.cpp b/producer/api/cpp/src/request_handler_tcp.cpp
index 157c1212e6b24089d7ed8ace19d7de3f2fc26da5..e6f105d0150499ad74f665b16610710c97153df0 100644
--- a/producer/api/cpp/src/request_handler_tcp.cpp
+++ b/producer/api/cpp/src/request_handler_tcp.cpp
@@ -13,12 +13,18 @@ RequestHandlerTcp::RequestHandlerTcp(ReceiverDiscoveryService* discovery_service
 }
 
 Error RequestHandlerTcp::Authorize(const std::string& source_credentials) {
-    GenericRequestHeader header{kOpcodeAuthorize, 0, 0, 0, source_credentials.c_str()};
+    GenericRequestHeader header{kOpcodeAuthorize, 0, 0, source_credentials.size(), ""};
     Error err;
     io__->Send(sd_, &header, sizeof(header), &err);
     if(err) {
         return err;
     }
+
+    io__->Send(sd_, (void*) source_credentials.c_str(), (size_t) header.meta_size, &err);
+    if (err) {
+        return err;
+    }
+
     return ReceiveResponse(header, nullptr);
 }
 
diff --git a/producer/api/cpp/unittests/test_request_handler_tcp.cpp b/producer/api/cpp/unittests/test_request_handler_tcp.cpp
index 25a88248bb4b2b3ed107704870670260d9a1699e..536aee478111030daf6181ddf82d475b5b8a877e 100644
--- a/producer/api/cpp/unittests/test_request_handler_tcp.cpp
+++ b/producer/api/cpp/unittests/test_request_handler_tcp.cpp
@@ -195,7 +195,7 @@ void RequestHandlerTcpTests::ExpectFailAuthorize(bool only_once) {
     int i = 0;
     for (auto expected_sd : expected_sds) {
         EXPECT_CALL(mock_io,
-                    Send_t(expected_sd, M_CheckSendRequest(asapo::kOpcodeAuthorize, 0, 0, expected_beamtime_id,
+                    Send_t(expected_sd, M_CheckSendRequest(asapo::kOpcodeAuthorize, 0, 0, "",
                                                                ""),
                            sizeof(asapo::GenericRequestHeader), _))
             .WillOnce(
@@ -203,6 +203,13 @@ void RequestHandlerTcpTests::ExpectFailAuthorize(bool only_once) {
                     testing::SetArgPointee<3>(nullptr),
                     Return(sizeof(asapo::GenericRequestHeader))
                 ));
+        EXPECT_CALL(mock_io,
+                    Send_t(expected_sd, _,strlen(expected_beamtime_id), _))
+            .WillOnce(
+                DoAll(
+                    testing::SetArgPointee<3>(nullptr),
+                    Return(strlen(expected_beamtime_id))
+                ));
 
         EXPECT_CALL(mock_io, Receive_t(expected_sd, _, sizeof(asapo::SendResponse), _))
             .InSequence(seq_receive[i])
@@ -236,7 +243,7 @@ void RequestHandlerTcpTests::ExpectOKAuthorize(bool only_once) {
     int i = 0;
     for (auto expected_sd : expected_sds) {
         EXPECT_CALL(mock_io,
-                    Send_t(expected_sd, M_CheckSendRequest(asapo::kOpcodeAuthorize, 0, 0, expected_beamtime_id,
+                    Send_t(expected_sd, M_CheckSendRequest(asapo::kOpcodeAuthorize, 0, 0, "",
                                                                ""),
                            sizeof(asapo::GenericRequestHeader), _))
             .WillOnce(
@@ -244,6 +251,13 @@ void RequestHandlerTcpTests::ExpectOKAuthorize(bool only_once) {
                     testing::SetArgPointee<3>(nullptr),
                     Return(sizeof(asapo::GenericRequestHeader))
                 ));
+        EXPECT_CALL(mock_io,
+                    Send_t(expected_sd, _,strlen(expected_beamtime_id), _))
+            .WillOnce(
+                DoAll(
+                    testing::SetArgPointee<3>(nullptr),
+                    Return(strlen(expected_beamtime_id))
+                ));
 
         EXPECT_CALL(mock_io, Receive_t(expected_sd, _, sizeof(asapo::SendResponse), _))
             .InSequence(seq_receive[i])