Can lcov/genhtml show files that were never executed?

How can I make lcov and genhtml show files that are not linked / loaded? I'm using it to show test coverage and I would like to see every source file appear in the HTML report, even if it has zero coverage. That way I can use lcov to identify source files that are missing tests. The missing source files have a .gcno file created for them, but not a .gcda file.