diff --git a/sys/contrib/dev/acpica/include/actypes.h b/sys/contrib/dev/acpica/include/actypes.h
--- a/sys/contrib/dev/acpica/include/actypes.h
+++ b/sys/contrib/dev/acpica/include/actypes.h
@@ -658,8 +658,13 @@
 /* Pointer/Integer type conversions */
 
 #define ACPI_TO_POINTER(i)              ACPI_CAST_PTR (void, (ACPI_SIZE) (i))
+#ifdef __FreeBSD__
+#define ACPI_TO_INTEGER(p)              ((ACPI_SIZE) (p))
+#define ACPI_OFFSET(d, f)               ((ACPI_SIZE) __offsetof(d, f))
+#else
 #define ACPI_TO_INTEGER(p)              ACPI_PTR_DIFF (p, (void *) 0)
 #define ACPI_OFFSET(d, f)               ACPI_PTR_DIFF (&(((d *) 0)->f), (void *) 0)
+#endif
 #define ACPI_PHYSADDR_TO_PTR(i)         ACPI_TO_POINTER(i)
 #define ACPI_PTR_TO_PHYSADDR(i)         ACPI_TO_INTEGER(i)