diff --git a/src/mainboard/prodrive/hermes/eeprom.c b/src/mainboard/prodrive/hermes/eeprom.c
index 4daef43b1d..70a163f882 100644
--- a/src/mainboard/prodrive/hermes/eeprom.c
+++ b/src/mainboard/prodrive/hermes/eeprom.c
@@ -127,10 +127,10 @@ struct eeprom_bmc_settings *get_bmc_settings(void)
 
 const char *eeprom_read_serial(const size_t offset, const char *const fallback)
 {
-	static char serial_no[HERMES_SN_PN_LENGTH] = { 0 };
+	static char serial_no[HERMES_SN_PN_LENGTH + 1] = { 0 };
 	memset(serial_no, 0, sizeof(serial_no));
 
-	if (eeprom_read_buffer(serial_no, offset, sizeof(serial_no)) == 0)
+	if (eeprom_read_buffer(serial_no, offset, HERMES_SN_PN_LENGTH) == 0)
 		return serial_no;
 	else
 		return fallback;