diff --git a/modbus.c b/modbus.c
index ddf37b6..1b03d13 100644
--- a/modbus.c
+++ b/modbus.c
@@ -157,6 +157,8 @@ static int8_t modbus_transaction_to_buffer(uint8_t *buffer, uint8_t *msg_len, mo
 				*msg_len = modbus_fill_device_id_objects(buffer+buffer_pos, transaction);
 				*msg_len += 7; /* includes 2 bytes for CRC */
 				break;
+			default:
+				break;
 		}
 	}
 	crc16 = modbus_CRC16(buffer, buffer_pos); /* last two bytes is the checksum itself */
@@ -240,7 +242,9 @@ static int8_t modbus_process_read_write_request(const uint8_t *buffer, int len,
 	case MODBUS_WRITE_MULTIPLE_AO:
 	case MODBUS_READ_WRITE_MULTIPLE_REGISTERS:
 		transaction->register_number = MODBUS_AO_START_NUMBER;
-		break;	
+		break;
+	default:
+		break;
 	}
 
 	#define MODBUS_FLAG_WRITE  0x01