NSRequiredContext in services

Our app has a service to open a URL or file path selected in some view. I have declared the service as described in the Info.plist, and that has always worked. I now added the new NSRequiredContext to the plist, as follows:

			<key>NSRequiredContext</key>
			<dict>
				<key>NSTextContent</key>
				<array>
					<string>URL</string>
					<string>FilePath</string>
				</array>
			</dict>

I ran pbs to update the services cache, and checked that it indeed uses the correct version of the services from the correct version of my app, including this NSRequiredContext. 

I also made sure that my service was checked in the Services system preferences. 

However, after this my service does not turn up anymore on the Services menu when I select a URL (string) or a (valid) file path, e.g. in TextEdit or Safari. 

Is there something wrong with my expectation, or is this just not supported properly?

thanks,
Christiaan