diff --git a/man/man3/ioproc.3 b/man/man3/ioproc.3
index 2d5bbd7..c0fd414 100644
--- a/man/man3/ioproc.3
+++ b/man/man3/ioproc.3
@@ -194,3 +194,9 @@
 .SH BUGS
 .I Iointerrupt
 is currently unimplemented.
+.PP
+C99 disallows the use of pointers to
+.BR va_list .
+This interface will have to change to
+use pointers to a structure containing a 
+.BR va_list .