diff --git a/drivers/acpi/acpica/aclocal.h b/drivers/acpi/acpica/aclocal.h
index 772ee5c4ccca..2ec394a328e9 100644
--- a/drivers/acpi/acpica/aclocal.h
+++ b/drivers/acpi/acpica/aclocal.h
@@ -787,7 +787,12 @@ struct acpi_bit_register_info {
 
 /* For control registers, both ignored and reserved bits must be preserved */
 
-#define ACPI_PM1_CONTROL_IGNORED_BITS           0x0201	/* Bits 9, 0(SCI_EN) */
+/*
+ * The ACPI spec says to ignore PM1_CTL.SCI_EN (bit 0)
+ * but we need to be able to write ACPI_BITREG_SCI_ENABLE directly
+ * as a BIOS workaround on some machines.
+ */
+#define ACPI_PM1_CONTROL_IGNORED_BITS           0x0200	/* Bits 9 */
 #define ACPI_PM1_CONTROL_RESERVED_BITS          0xC1F8	/* Bits 14-15, 3-8 */
 #define ACPI_PM1_CONTROL_PRESERVED_BITS \
 	       (ACPI_PM1_CONTROL_IGNORED_BITS | ACPI_PM1_CONTROL_RESERVED_BITS)