New installs or profiles of Firefox 31.0 refuse to install the spelling dictionary Nederlands with: "Not available for Firefox 31.0", which is silly because the dictionary in question is working just fine in existing versions of Firefox (where this spelling dictionary was installed earlier) that have been updated to 31.0 .

How do I get Firefox to install the dictionary anyway/? I have this problem with a new install on my laptop (Ubuntu Linux) and a new profile on my PC (Slackware Linux).