We have: ... auto networkSession = getNetworkSession(); ... getNetworkSession() can return non-null pointer even if networkSessionStrongRef is null: ... if (networkSessionStrongRef) return networkSessionStrongRef; return networkSessionWeakRef.toStrongRef(); .... We check the result: if (networkSession) { // here we disconnect signals } But we should use the same networkSession when disconnecting, not start using networkSessionStrongRef suddenly, since it can be null. Task-number: QTBUG-57110 Change-Id: I96babb42c2182e741e6eabaf7d1abb88869861f4 Reviewed-by: Jesus Fernandez <jesus.fernandez@qt.io> Reviewed-by: Edward Welbourne <edward.welbourne@qt.io> Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>