Spring Webflow transition executing twice

When I call the js function that should execute a certain spring transition, the transition executes twice in chrome (only one call to javascript function is processed).

This is my javascript:

function sort(by) {
  window.location.href = flowExecutionUrl + "&_eventId=sort&mode=" + by;  
}

T开发者_StackOverflow社区his is my view state:

<view-state id="details" view="details">
    <transition on="sort">
        expression="dataService.sort(requestParameters.mode)
        result="viewScope.data" />
    </transition>
</view-state>

Any thought? I am out of ideas at the moment