diff --git a/include/acpi/acpixf.h b/include/acpi/acpixf.h
index c9b903f..be0aa5e 100644
--- a/include/acpi/acpixf.h
+++ b/include/acpi/acpixf.h
@@ -48,6 +48,8 @@
 #include "actypes.h"
 #include "actbl.h"
 
+extern u8 acpi_gbl_permanent_mmap;
+
 /*
  * Global interfaces
  */