     
     private func exchangeMTU(_ pdu: ATTMaximumTransmissionUnitRequest) {
         
-        let serverMTU = connection.maximumTransmissionUnit.rawValue
+        let serverMTU = preferredMaximumTransmissionUnit.rawValue
         
         let finalMTU = ATTMaximumTransmissionUnit(server: serverMTU, client: pdu.clientMTU)
         

        
        // set initial MTU and register handlers
        self.maximumPreparedWrites = maximumPreparedWrites
        self.connection = ATTConnection(socket: socket)
        self.connection.maximumTransmissionUnit = maximumTransmissionUnit
        self.registerATTHandlers()
    }
    

    
    public let maximumPreparedWrites: Int
    
    public private(set) var maximumTransmissionUnit: ATTMaximumTransmissionUnit = .default {
        
        // update connection with new value
        didSet { connection.maximumTransmissionUnit = maximumTransmissionUnit }
    }
    
    public let preferredMaximumTransmissionUnit: ATTMaximumTransmissionUnit
    
    // Don't modify
    @_versioned
