diff --git a/tests/auto/qtcpsocket/qtcpsocket.pro b/tests/auto/qtcpsocket/qtcpsocket.pro
index 5dfff5bb88..48ac1fa0c5 100644
--- a/tests/auto/qtcpsocket/qtcpsocket.pro
+++ b/tests/auto/qtcpsocket/qtcpsocket.pro
@@ -6,3 +6,5 @@ wince*|symbian|vxworks* : SUBDIRS = test
 
 
 requires(contains(QT_CONFIG,private_tests))
+
+CONFIG+=insignificant_test  # unstable, QTBUG-21043