diff --git a/src/main.rs b/src/main.rs
index 951f70a..7146a7b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -59,6 +59,10 @@ impl file_rpc::Server for FileServ {
     fn size(&self, _fd: u64) -> Option<u64> {
         None
     }
+
+    fn dup(&self, fd: u64) -> Option<u64> {
+        Some(fd)
+    }
 }
 
 fn main() {