diff --git a/tests/HDF5WritingTest.cpp b/tests/HDF5WritingTest.cpp
index bc18fc1a3..23e9fabb7 100644
--- a/tests/HDF5WritingTest.cpp
+++ b/tests/HDF5WritingTest.cpp
@@ -5,6 +5,7 @@
 #include <iostream>
 #include <fstream>
 #include <filesystem>
+#include <thread>
 
 #include "../common/DiffractionExperiment.h"
 #include "../writer/HDF5Objects.h"
@@ -573,6 +574,10 @@ TEST_CASE("HDF5Writer_Socket", "[HDF5][Full]") {
         s.SubscribeAll();
         s.ReceiveTimeout(std::chrono::seconds(5));
 
+        // PUB drops what it sends before the subscription has reached it, and the first file is closed
+        // (and announced) right after the second image - ensure sub socket is properly connected
+        std::this_thread::sleep_for(std::chrono::seconds(2));
+
         for (int i = 0; i < x.GetImageNum(); i++) {
             DataMessage message{};
             message.image = CompressedImage(image,  x.GetXPixelsNum(), x.GetYPixelsNum());