diff --git a/src/os/win32/ngx_files.c b/src/os/win32/ngx_files.c
index 7695198..2d89890 100644
--- a/src/os/win32/ngx_files.c
+++ b/src/os/win32/ngx_files.c
@@ -501,3 +501,10 @@
 
     return NGX_OK;
 }
+
+
+ngx_int_t
+ngx_directio(ngx_fd_t fd)
+{
+    return 0;
+}
diff --git a/src/os/win32/ngx_files.h b/src/os/win32/ngx_files.h
index 5973e95..294709f 100644
--- a/src/os/win32/ngx_files.h
+++ b/src/os/win32/ngx_files.h
@@ -216,7 +216,7 @@
     off_t offset, ngx_pool_t *pool);
 
 
-#define ngx_directio(fd)            0
+ngx_int_t ngx_directio(ngx_fd_t fd);
 #define ngx_directio_n              "ngx_directio_n"