diff --git a/lib/perfdata/elasticsearchwriter.cpp b/lib/perfdata/elasticsearchwriter.cpp
index 7a7d6f18c..f8e7140ea 100644
--- a/lib/perfdata/elasticsearchwriter.cpp
+++ b/lib/perfdata/elasticsearchwriter.cpp
@@ -118,7 +118,11 @@ void ElasticsearchWriter::Pause()
 	m_HandleNotifications.disconnect();
 
 	m_WorkQueue.Join();
-	Flush();
+
+	{
+		std::unique_lock<std::mutex> lock (m_DataBufferMutex);
+		Flush();
+	}
 
 	Log(LogInformation, "ElasticsearchWriter")
 		<< "'" << GetName() << "' paused.";