MacOS X 10.3, FreeBSD 6.0, NetBSD 1.6, OpenBSD 3.8, OSF/1 5.1.
@item
On some platforms, this function does not fail with @samp{EINVAL} when
-passed a null pointer, an empty string, or a string containing @samp{=}:
+passed an empty string or a string containing @samp{=}:
FreeBSD 6.0, NetBSD 1.6, OpenBSD 3.8.
@item
This function removes only the first value association for the given
Portability problems not fixed by Gnulib:
@itemize
+@item
+Older versions of POSIX required that @code{unsetenv(NULL)} gracefully
+fail with @code{EINVAL}, but not all implementations guarantee this,
+and the requirement was removed.
@end itemize