diff --git a/src/os/unix/ngx_files.c b/src/os/unix/ngx_files.c
index 417b598..36b6b67 100644
--- a/src/os/unix/ngx_files.c
+++ b/src/os/unix/ngx_files.c
@@ -226,6 +226,7 @@
             return NGX_ERROR;
         }
 
+        file->sys_offset += n;
         file->offset += n;
         written += n;