diff --git a/src/os/unix/ngx_files.h b/src/os/unix/ngx_files.h
index ccaf44a..f41eba5 100644
--- a/src/os/unix/ngx_files.h
+++ b/src/os/unix/ngx_files.h
@@ -64,6 +64,7 @@
 #define NGX_FILE_OPEN            0
 #define NGX_FILE_TRUNCATE        O_CREAT|O_TRUNC
 #define NGX_FILE_APPEND          O_WRONLY|O_APPEND
+#define NGX_FILE_NONBLOCK        O_NONBLOCK
 
 #define NGX_FILE_DEFAULT_ACCESS  0644
 #define NGX_FILE_OWNER_ACCESS    0600