diff --git a/man2/ioperm.2 b/man2/ioperm.2
index 863b4df0a..917c10774 100644
--- a/man2/ioperm.2
+++ b/man2/ioperm.2
@@ -45,9 +45,16 @@ ioperm \- set port input/output permissions
 .SH DESCRIPTION
 .BR ioperm ()
 sets the port access permission bits for the calling thread for
-\fInum\fP bits starting from port address \fIfrom\fP to the value
-\fIturn_on\fP.
-If \fIturn_on\fP is nonzero, the calling thread must be privileged
+.I num
+bits starting from port address
+.IR from .
+If 
+.I turn_on
+is nonzero, then permission for the specified bits is enabled;
+otherwise it is disabled.
+If
+.I turn_on
+is nonzero, the calling thread must be privileged
 .RB ( CAP_SYS_RAWIO ).
 
 Before Linux 2.6.8,