setInterval - ti\bootstrap.js - Uncaught Error: Invalid value, expected type Number.

I've got the below function which acts as a timer in my code:

var countDown =  function( m , s, fn_tick, fn_end  ) {
    return {
        total_sec:m*60+s,
        timer:this.timer,
        set: function(m,s) {
            this.total_sec = parseInt(m)*60+parseInt(s);
            this.time = {m:m,s:s};
            return this;
        },
        start: function() {
            var self = this;
            this.timer = setInterval( function() {
                if (self.total_sec) {
                    self.total_sec--;
                    fn_tick();
                }
                else {
                    self.stop();
                    fn_end();
                }
                }, 1000 );
            return this;
        },
        stop: function() {
            clearInterval(this.timer);
            this.time = {m:0,s:0};
            this.total_sec = 0;
            return this;
        }
    };
};

However i get the below error when it runs for the first time:

In ti:/bootstrap.js:131,32
Message: Uncaught Error: Invalid value, expected type Number.
Source: return Titanium.clearTimeout.apply(Titanium, arguments);

I found a ticket that is open about this issue https://jira.appcelerator.org/browse/TIMOB-14213 which suggessts that i need to nullify the setInterval variable before running however if I do this.timer = null it makes no difference

Running on Android with latest SDK on Alloy