Configure alternative value assignment fails

configure --help

Conventions for the remaining options: When an option's description is
followed by a list of values in brackets, the interpretation is as follows:
'yes' represents the bare option; all other values are possible prefixes to
the option, e.g., -no-gui. Alternatively, the value can be assigned, e.g.,
--gui=yes. Values are listed in the order they are tried if not specified;
'auto' is a shorthand for 'yes/no'. Solitary 'yes' and 'no' represent binary
options without auto-detection.

configure -opensource -confirm-license --gui=yes
...

Creating qmake...
.Done.

ERROR: Unknown command line option '--gui=yes'.