--- a/ext/posix/posix.c
+++ b/ext/posix/posix.c
@@ -541,7 +541,7 @@ PHP_FUNCTION(posix_uname)
 	add_assoc_string(return_value, "version",  u.version,  1);
 	add_assoc_string(return_value, "machine",  u.machine,  1);
 #ifdef _GNU_SOURCE
-	add_assoc_string(return_value, "domainname", u.domainname, 1);
+	add_assoc_string(return_value, "domainname", u.__domainname, 1);
 #endif
 }
 /* }}} */