diff --git a/lib/pairing.js b/lib/pairing.js
index 00916abe..929231fa 100644
--- a/lib/pairing.js
+++ b/lib/pairing.js
@@ -5,6 +5,10 @@ const db = require('./db')
 const options = require('./options')
 const logger = require('./logger')
 
+// A machine on an older version (no multicassette code) could be paired with a server with multicassette code.
+// This makes sure that the server stores a default value
+const DEFAULT_NUMBER_OF_CASSETTES = 2 
+
 function pullToken (token) {
   const sql = `delete from pairing_tokens
     where token=$1
@@ -20,7 +24,7 @@ function unpair (deviceId) {
   return Promise.all([db.none(sql, [deviceId]), db.none(deleteMachinePings, [deviceId])])
 }
 
-function pair (token, deviceId, machineModel, numOfCassettes) {
+function pair (token, deviceId, machineModel, numOfCassettes = DEFAULT_NUMBER_OF_CASSETTES) {
   return pullToken(token)
     .then(r => {
       if (r.expired) return false