diff --git a/grub-core/kern/file.c b/grub-core/kern/file.c
index 3367485fb..668f8930b 100644
--- a/grub-core/kern/file.c
+++ b/grub-core/kern/file.c
@@ -89,6 +89,11 @@ grub_file_open (const char *name)
 
   file->device = device;
 
+  /* In case of relative pathnames and non-Unix systems (like Windows)
+   * name of host files may not start with `/'. Blocklists for host files
+   * are meaningless as well (for a start, host disk does not allow any direct
+   * access - it is just a marker). So skip host disk in this case.
+   */
   if (device->disk && file_name[0] != '/'
 #if defined(GRUB_UTIL) || defined(GRUB_MACHINE_EMU)
       && grub_strcmp (device->disk->name, "host")