diff --git a/io/io_sendfile.c b/io/io_sendfile.c
index 96b5b2a..428aa40 100644
--- a/io/io_sendfile.c
+++ b/io/io_sendfile.c
@@ -19,7 +19,7 @@ int64 io_sendfile(int64 s,int64 fd,uint64 off,uint64 n) {
     io_eagain_write(s);
     return (errno==EAGAIN?(sbytes?sbytes:-1):-3);
   }
-  if (sbytes<ct)
+  if ((uint64)sbytes<(uint64)ct)
     io_eagain_write(s);
   return n;
 }