diff --git a/drivers/acpi/system.c b/drivers/acpi/system.c
index 743f244..4aaf249 100644
--- a/drivers/acpi/system.c
+++ b/drivers/acpi/system.c
@@ -25,6 +25,7 @@
 
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
+#include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/string.h>
 #include <asm/uaccess.h>