diff --git a/netroute_windows.go b/netroute_windows.go
index 505c2e3..67c5014 100644
--- a/netroute_windows.go
+++ b/netroute_windows.go
@@ -193,12 +193,18 @@ func getIface(index uint32) *net.Interface {
 		return nil
 	}
 
+	physAddrLen := int(ifRow.PhysAddrLen)
+	if len(ifRow.PhysAddr) < physAddrLen && physAddrLen >= 0 {
+		physAddrLen = len(ifRow.PhysAddr)
+	}
+	physAddr := ifRow.PhysAddr[:physAddrLen]
+
 	ifaces, err := net.Interfaces()
 	if err != nil {
 		return nil
 	}
 	for _, iface := range ifaces {
-		if bytes.Equal(iface.HardwareAddr, ifRow.PhysAddr[:]) {
+		if bytes.Equal(iface.HardwareAddr, physAddr) {
 			return &iface
 		}
 	}