diff --git a/net/cpp/src/universe.cpp b/net/cpp/src/universe.cpp
index f6d7e2acba34e6fde82b07a6db7064555512c303..e2bb8d8caca3e4f693a86c1aa27d93ee83b53d2e 100644
--- a/net/cpp/src/universe.cpp
+++ b/net/cpp/src/universe.cpp
@@ -227,6 +227,8 @@ void Universe::_run() {
 			continue;
 		}
 
+		unique_lock<mutex> lk(net_mutex_);
+
 		//If connection request is waiting
 		for (auto l : listeners_) {
 			if (l && l->isListening()) {