Can't specify URLs via --open=

Jalview seems to process '/' differently when it is passed via JVL:

This works:
jalview.apparg=--open
jalview.apparg=https://www.jalview.org/examples/plantfdx.fa

Whereas this does not:
jalview.apparg=--open=https://www.jalview.org/examples/plantfdx.fa

The same is true on the command line:
jalview --open=https://www.jalview.org/examples/plantfdx.fa

In all cases '=' form seems to result in the protocol://location being corrupted:

ERROR - Can't find file 'https:/www.jalview.org/examples/plantfdx.fa'
Exception in thread "main" java.lang.NullPointerException
at jalview.bin.Commands.processLinked(Commands.java:504)
at jalview.bin.Commands.processArgs(Commands.java:132)
at jalview.bin.Jalview.doMain(Jalview.java:862)
at jalview.bin.Jalview.main(Jalview.java:259)