diff --git a/src/cloud.rs b/src/cloud.rs
index 5a0d0fe..d056b72 100644
--- a/src/cloud.rs
+++ b/src/cloud.rs
@@ -591,7 +591,7 @@ impl<P: Protocol> GenericCloud<P> {
                         }
                     },
                     fd if (fd == device_fd) => {
-                        let start = 64;
+                        let mut start = 64;
                         let (offset, size) = try_fail!(self.device.read(&mut buffer[start..]), "Failed to read from tap device: {}");
                         start += offset;
                         if let Err(e) = self.handle_interface_data(&mut buffer, start, start+size) {