diff --git a/man3/lseek64.3 b/man3/lseek64.3
index 9325203e1..732c39fa5 100644
--- a/man3/lseek64.3
+++ b/man3/lseek64.3
@@ -170,6 +170,18 @@ system call.
 Instead, they have an
 .BR lseek (2)
 system call that supports 64-bit file offsets.
+.\" In arch/x86/entry/syscalls/syscall_32.tbl,
+.\" we see the following line:
+.\"
+.\"    140     i386    _llseek                 sys_llseek
+.\"
+.\" This is essentially telling us that 'sys_llseek' (the name generated
+.\" by SYSCALL_DEFINE5(llseek...)) is exposed to user-space as system call
+.\" number 140, and that system call number will (IIUC) be exposed in
+.\" autogenerated headers with the name "__NR__llseek" (i.e., "_llseek").
+.\" The "i386" is telling us that this happens in i386 (32-bit Intel).
+.\" There is nothing equivalent on x86-64, because 64 bit systems don't
+.\" need an _llseek system call.
 .SH ATTRIBUTES
 For an explanation of the terms used in this section, see
 .BR attributes (7).