diff --git a/drivers/acpi/ac.c b/drivers/acpi/ac.c
index b6ed60b..56205a0 100644
--- a/drivers/acpi/ac.c
+++ b/drivers/acpi/ac.c
@@ -25,6 +25,7 @@
 
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/types.h>
 #ifdef CONFIG_ACPI_PROCFS_POWER