diff --git a/lib/libc/sys/read.2 b/lib/libc/sys/read.2
index 1e98f3a3bb6..b3dfa925572 100644
--- a/lib/libc/sys/read.2
+++ b/lib/libc/sys/read.2
@@ -32,7 +32,7 @@
 .\"     @(#)read.2	8.4 (Berkeley) 2/26/94
 .\" $FreeBSD$
 .\"
-.Dd February 26, 1994
+.Dd October 16, 2004
 .Dt READ 2
 .Os
 .Sh NAME
@@ -215,7 +215,7 @@ The
 system call may also return the following errors:
 .Bl -tag -width Er
 .It Bq Er EINVAL
-The specified file offset is invalid.
+The specified file offset is invalid, i.e. negative.
 .It Bq Er ESPIPE
 The file descriptor is associated with a pipe, socket, or FIFO.
 .El
diff --git a/lib/libc/sys/write.2 b/lib/libc/sys/write.2
index 4687e3bab6a..55389c0a48f 100644
--- a/lib/libc/sys/write.2
+++ b/lib/libc/sys/write.2
@@ -32,7 +32,7 @@
 .\"     @(#)write.2	8.5 (Berkeley) 4/2/94
 .\" $FreeBSD$
 .\"
-.Dd April 2, 1994
+.Dd October 16, 2004
 .Dt WRITE 2
 .Os
 .Sh NAME
@@ -231,7 +231,7 @@ The
 system call may also return the following errors:
 .Bl -tag -width Er
 .It Bq Er EINVAL
-The specified file offset is invalid.
+The specified file offset is invalid, i.e. negative.
 .It Bq Er ESPIPE
 The file descriptor is associated with a pipe, socket, or FIFO.
 .El