diff --git a/net_util/src/tap.rs b/net_util/src/tap.rs
index f361b5003..7c701d6b3 100644
--- a/net_util/src/tap.rs
+++ b/net_util/src/tap.rs
@@ -396,7 +396,9 @@ mod tests {
     // For a given interface name, this returns a tuple that contains the MAC address of the
     // interface, an object that can be used to send Ethernet frames, and a receiver of
     // Ethernet frames arriving at the specified interface.
-    fn pnet_get_mac_tx_rx(ifname: String) -> (MacAddr, Box<DataLinkSender>, Box<DataLinkReceiver>) {
+    fn pnet_get_mac_tx_rx(
+        ifname: String,
+    ) -> (MacAddr, Box<dyn DataLinkSender>, Box<dyn DataLinkReceiver>) {
         let interface_name_matches = |iface: &NetworkInterface| iface.name == ifname;
 
         // Find the network interface with the provided name.