diff --git a/drivers/acpi/acpica/Makefile b/drivers/acpi/acpica/Makefile
index 8bb43f06e11fda07c6e71718fab7b2baa37a5a57..87a24ac213635ebd784fbaa4a2d7415775ad6d3a 100644
--- a/drivers/acpi/acpica/Makefile
+++ b/drivers/acpi/acpica/Makefile
@@ -2,7 +2,7 @@
 # Makefile for ACPICA Core interpreter
 #
 
-ccflags-y			:= -Os
+ccflags-y			:= -Os -DBUILDING_ACPICA
 ccflags-$(CONFIG_ACPI_DEBUG)	+= -DACPI_DEBUG_OUTPUT
 
 # use acpi.o to put all files here into acpi.o modparam namespace
diff --git a/include/acpi/platform/aclinux.h b/include/acpi/platform/aclinux.h
index dfba35476b8ad726fd3e0f4d92a93a7a16eca674..1ba7c190c2ccbfc22ca9f576a0f7faf9ef96d979 100644
--- a/include/acpi/platform/aclinux.h
+++ b/include/acpi/platform/aclinux.h
@@ -44,6 +44,16 @@
 #ifndef __ACLINUX_H__
 #define __ACLINUX_H__
 
+#ifdef __KERNEL__
+
+/* ACPICA external files should not include ACPICA headers directly. */
+
+#if !defined(BUILDING_ACPICA) && !defined(_LINUX_ACPI_H)
+#error "Please don't include <acpi/acpi.h> directly, include <linux/acpi.h> instead."
+#endif
+
+#endif
+
 /* Common (in-kernel/user-space) ACPICA configuration */
 
 #define ACPI_USE_SYSTEM_CLIBRARY