webkit transitions not working in chrome and safari

Question

I'm having trouble getting a transition to work in webkit browsers, while it works perfectly in firefox. My code is below

HTML
<div class="dropdown" data-id="new-houses">
<h3>New Houses</h3>
<img src="/local/images/down-arrow.png" />
</div>
<div id="new-houses" style="display:none;">
<!--content of div-->
</div>

CSS
.dropdown{
   width:100%;
   cursor:pointer;
   height:50px;
   clear:both;
}
.dropdown img{
    width:20px;
    height:17px;
    float:right;
    margin-right:20px;
    margin-top:17px;
    -webkit-transition:transform 1s;
    -moz-transition:transform 1s;
    -ms-transition:transform 1s;
    -o-transition:transform 1s;
    transition:transform 1s;
}
.point_down{
    transform:rotate(180deg);
    -webkit-transform:rotate(180deg);
    -moz-transform:rotate(180deg);
    -ms-transform:rotate(180deg);
    -o-transform:rotate(180deg);
}

jQuery
$('.dropdown').click(function(){
    var self = $(this);
    self.find('img').toggleClass('point_down');
    $('#'+self.attr('data-id')).slideToggle(1000);
});

The transform is working in FF, Safari and Chrome, but the transition only works with FF. I have tried changing the img to both inline-block and block, which made no difference I could see. Has anyone encountered this before, or can see if there's anything wrong with my code? Any help you can offer will be much appreciated.

Solution

It's

-webkit-transition:-webkit-transform 1s;