diff --git a/man2/ioperm.2 b/man2/ioperm.2
index 4c52b2638..37e1d0a7e 100644
--- a/man2/ioperm.2
+++ b/man2/ioperm.2
@@ -35,9 +35,6 @@
 .SH NAME
 ioperm \- set port input/output permissions
 .SH SYNOPSIS
-.B #include <unistd.h>
-/* for libc5 */
-.br
 .B #include <sys/io.h>
 /* for glibc */
 .sp
@@ -110,10 +107,9 @@ The
 .I /proc/ioports
 file shows the I/O ports that are currently allocated on the system.
 
-Libc5 treats it as a system call and has a prototype in
-.IR <unistd.h> .
-Glibc1 does not have a prototype.
-Glibc2 has a prototype both in
+Glibc has an
+.BR ioperm ()
+prototype both in
 .I <sys/io.h>
 and in
 .IR <sys/perm.h> .