many 'g_environ_setenv: assertion 'value != NULL' failed' in journal

I'm seeing a lot of these messages in the journal under Gnome 3.32.1 using Ubuntu, Fedora and Pop OS. The messages are like this one:

gnome-shell[3511]: g_environ_setenv: assertion 'value != NULL' failed

Happens every time I open an app like Gnome Settings. No extensions enabled.