DISM: "The source files could not be found and download failed"

Trying to install a selection of IIS Windows features via dism:

dism /NoRestart /ONLINE /Enable-Feature /All /FeatureName:IIS
-ASPNET /FeatureName:IIS-NetFxExtensibility /FeatureName:WCF-HTTP-Activation

gives the error

Error: 0x800f0906

The source files could not be downloaded. Use the "source" option to specify the location of the files that are required t o restore the feature. For more information on specifying a source location, see http://go.microsoft.com/fwlink/?LinkId=243077.

The DISM log file can be found at C:\WINDOWS\Logs\DISM\dism.log

The features IIS-NetFxExtensibility, IIS-ASPNET and IIS-NetFxExtensibility are for .NET 3.5 and are restricted for security reasons.

I really wanted .NET 4.5 anyway, so fixed by appending 45 to those feature names

dism /NoRestart /ONLINE /Enable-Feature /All  /FeatureName:IIS
-ASPNET45 /FeatureName:IIS-NetFxExtensibility45 /FeatureName:WCF-HTTP-Activation /FeatureName:WCF-HTTP-Activation45