diff --git a/src/DirectCommunicationClient.cpp b/src/DirectCommunicationClient.cpp
index 78b8f25..98f05e5 100644
--- a/src/DirectCommunicationClient.cpp
+++ b/src/DirectCommunicationClient.cpp
@@ -54,7 +54,7 @@ namespace DirectCommunication
             receivedMessages_.get(msg);
             return msg;
         }
-        return nullptr;
+        return "NULL";
     }
 
     void DirectCommunicationClient::workerFunc_()
diff --git a/src/DirectCommunicationServer.cpp b/src/DirectCommunicationServer.cpp
index ad0a0e8..43aaf17 100644
--- a/src/DirectCommunicationServer.cpp
+++ b/src/DirectCommunicationServer.cpp
@@ -55,7 +55,7 @@ namespace DirectCommunication
             receivedMessages_.get(msg);
             return msg;
         }
-        return nullptr;
+        return "NULL";
     }
 
     int DirectCommunicationServer::countClients()