diff --git a/include/acpi/acmacros.h b/include/acpi/acmacros.h
index 192fa09..9b2e4d7 100644
--- a/include/acpi/acmacros.h
+++ b/include/acpi/acmacros.h
@@ -55,6 +55,7 @@
 #define ACPI_SET_BIT(target,bit)        ((target) |= (bit))
 #define ACPI_CLEAR_BIT(target,bit)      ((target) &= ~(bit))
 #define ACPI_MIN(a,b)                   (((a)<(b))?(a):(b))
+#define ACPI_MAX(a,b)                   (((a)>(b))?(a):(b))
 
 /* Size calculation */