diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
index 717a29810473894aaf2f22e6e487f84087628df5..dad8af3ebeb5405c144db72cea488d7f5ea5fd39 100644
--- a/include/acpi/cppc_acpi.h
+++ b/include/acpi/cppc_acpi.h
@@ -133,6 +133,5 @@ extern int acpi_get_psd_map(struct cpudata **);
 /* Methods to interact with the PCC mailbox controller. */
 extern struct mbox_chan *
 	pcc_mbox_request_channel(struct mbox_client *, unsigned int);
-extern int mbox_send_message(struct mbox_chan *chan, void *mssg);
 
 #endif /* _CPPC_ACPI_H*/