MQTT sensor item not showing up in sitemap

I have created a new item using the MQTT binding as follows:

Number inside_temperature "temp [%.1f]" {mqtt="<[mosquitto:niek/climate/temperature-inside:state:default]"}

This seems to work fine, when I log into the console, smarthome:items shows me the following:

inside_temperature (Type=NumberItem, State=23.00, Label=temp, Category=null)

Next, I created my sitemap, with a text label for debugging:

sitemap niek label="Niek"
    Text label="Testing"
    Number item=inside_temperature label="Indoor temperature"

This however only shows me the text. Is there anything I’m doing wrong?

Try Text item=inside_temperature label=“Indoor temperature”

D’oh! I’m not sure where I found “Number”, but it is obviously not a valid type for sitemaps.