diff --git a/src/os/unix/ngx_files.c b/src/os/unix/ngx_files.c
index 65c79a241..7fbb7c9a7 100644
--- a/src/os/unix/ngx_files.c
+++ b/src/os/unix/ngx_files.c
@@ -356,6 +356,11 @@ ngx_chain_to_iovec(ngx_iovec_t *vec, ngx_chain_t *cl)
     n = 0;
 
     for ( /* void */ ; cl; cl = cl->next) {
+
+        if (ngx_buf_special(cl->buf)) {
+            continue;
+        }
+
         size = cl->buf->last - cl->buf->pos;
 
         if (prev == cl->buf->pos) {