diff --git a/src/pkg/net/tcpsockopt_darwin.go b/src/pkg/net/tcpsockopt_darwin.go
index d052a14..3314084 100644
--- a/src/pkg/net/tcpsockopt_darwin.go
+++ b/src/pkg/net/tcpsockopt_darwin.go
@@ -14,7 +14,7 @@
 
 // Set keep alive period.
 func setKeepAlivePeriod(fd *netFD, d time.Duration) error {
-	if err := fd.incref(false); err != nil {
+	if err := fd.incref(); err != nil {
 		return err
 	}
 	defer fd.decref()