Why is my browserify task appending the end of an exports twice

I am having an issue with my browserify task.

For some reason my browserify task keeps appending the following to the end and I can't see why

, format);
        };
    });
    },{}]},{},[1])

this is the Task:

gulp.task('browserify', function() {
        return browserify(sourceFile, {debug:true})
            .bundle()
            .pipe(source(destFile))
            .pipe(gulp.dest(destFolder));
    });

and This is the result:

12:[function(require,module,exports){
'use strict';

module.exports = (function ($filter){
    return function(input, format){
        return $filter('date')(new Date(input *1000), format);
    };
});
},{}]},{},[1])), format);
    };
});
},{}]},{},[1])

But my watchify task works fine. This is the task

gulp.task('watch-browserify', function() {
        var bundler = watchify(sourceFile, {debug:true});
        bundler.on('update', rebundle);

        function rebundle() {
            return bundler.bundle()
                .pipe(source(destFile))
                .pipe(gulp.dest(destFolder));
        }

        return rebundle();
    });

And this is the result:

12:[function(require,module,exports){
'use strict';

module.exports = (function ($filter){
    return function(input, format){
        return $filter('date')(new Date(input *1000), format);
    };
});

},{}]},{},[1])

Even if I remove the file contents of the file I still get

},{}]},{},[1])e,module,exports){

},{}]},{},[1])

Can help anyone can offer would be great