diff --git a/include/acpi/processor.h b/include/acpi/processor.h
index 06480bc..06ebb6e 100644
--- a/include/acpi/processor.h
+++ b/include/acpi/processor.h
@@ -319,6 +319,7 @@
 #endif				/* CONFIG_CPU_FREQ */
 
 /* in processor_throttling.c */
+int acpi_processor_tstate_has_changed(struct acpi_processor *pr);
 int acpi_processor_get_throttling_info(struct acpi_processor *pr);
 extern int acpi_processor_set_throttling(struct acpi_processor *pr, int state);
 extern struct file_operations acpi_processor_throttling_fops;