Clang warning about enum function prototype [closed]

While compiling certain piece of code that uses enum, I see following compiler(clang version 11.0.0, cross aarch64) warning:

    warning: cannot understand function prototype: 'enum xyz '

It's just normal enum:

enum xyz {    a = 0,    b         };

Same piece of code doesn't emit any such warning when GCC 7.3 is used.

ASAIK, in C enum can not have forward declaration.

So, is it just a bogus warning or there a way to solve it ?