[TYPO3-mvc] problem with submit of file upload

[Domi]

Hello,

I am confused because something simple doesn't work. I have a small 
upload form for an image:

<f:form enctype="multipart/form-data" name="client" action="updateFile"
arguments="{property:property, client:client}" method="POST">

<div>
	<input type="file" name="tx_intranet_frontend[{property}]"/>
</div>
					
<div>

	<f:form.submit value="upload"/>
</div>
</f:form>


- Controller ClientController exist
- action updateFileAction exist
- action is allowed inside of ext_localconf.php for the plugin

What is missing, that the submit of the form still doesn't reach the 
action updateFileAction? I have no idea where it goes, this is the 
generated link and it looks fine for me:

&tx_intranet_intranet%5Bproperty%5D=image&tx_intranet_intranet%5Baction%5D=updateFile&tx_intranet_intranet%5Bcontroller%5D=Client&cHash=69d2f816ff2604eeab2136e8bd3518fd


Thanks for any hint!

Cheers Dominic