diff --git a/drivers/mailbox/scpi_protocol.c b/drivers/mailbox/scpi_protocol.c
index 0404743fc617..771746396501 100644
--- a/drivers/mailbox/scpi_protocol.c
+++ b/drivers/mailbox/scpi_protocol.c
@@ -48,7 +48,7 @@
 #define DVFS_LATENCY(hdr)	((hdr) >> 16)
 #define DVFS_OPP_COUNT(hdr)	(((hdr) >> 8) & 0xff)
 
-int max_chan_num = 0;
+static int max_chan_num = 0;
 static DECLARE_BITMAP(bm_mbox_chans, 4);
 static DEFINE_MUTEX(scpi_mtx);