diff --git a/netstack/src/scheme/mod.rs b/netstack/src/scheme/mod.rs
index 18e2cc2a8e..8b0a6a141a 100644
--- a/netstack/src/scheme/mod.rs
+++ b/netstack/src/scheme/mod.rs
@@ -178,9 +178,11 @@ impl Smolnetd {
             } else {
                 name
             };
-            let mut link = EthernetLink::new(&dev_name, // SAFETY: caller must verify the safety contract for this operation
-unsafe {
-                File::from_raw_fd(nf.into_raw() as RawFd)
+            let mut link = EthernetLink::new(&dev_name, // SAFETY: caller guarantees nf is a live Fd not aliased
+                                       // elsewhere; from_raw_fd transfers ownership
+                                       // to the new File.
+            unsafe {
+                File::from_raw_fd(nf.into_raw())
             });
             link.set_mac_address(hw_addr);
             devices.borrow_mut().push(link);
@@ -191,8 +193,10 @@ unsafe {
             router_device: network_device,
             socket_set: Rc::clone(&socket_set),
             timer: ::std::time::Instant::now(),
-            time_file: // SAFETY: caller guarantees fd is valid, open, and not aliased
-unsafe { File::from_raw_fd(time_file.into_raw() as RawFd) },
+            time_file: // SAFETY: caller guarantees time_file is a live Fd not
+                     // aliased elsewhere; from_raw_fd transfers ownership
+                     // to the new File.
+            unsafe { File::from_raw_fd(time_file.into_raw()) },
             ip_scheme: IpScheme::new(
                 "ip",
                 Rc::clone(&iface),