--- a/dev-qt/qtcore/metadata.xml	
+++ a/dev-qt/qtcore/metadata.xml	
@@ -6,6 +6,7 @@ 
 		<name>Gentoo Qt Project</name>
 	</maintainer>
 	<use>
+		<flag name="old-kernel">disable new syscalls for Linux kernel >= 3.17</flag>
 		<flag name="systemd">Enable native journald logging support</flag>
 	</use>
 	<upstream>