diff --git a/bin/nproc/nproc.1 b/bin/nproc/nproc.1
index 91a87b1ca048..8ebe94a21049 100644
--- a/bin/nproc/nproc.1
+++ b/bin/nproc/nproc.1
@@ -3,7 +3,7 @@
 .\"
 .\" * SPDX-License-Identifier: BSD-2-Clause
 .\"
-.Dd February 5, 2023
+.Dd February 15, 2023
 .Dt NPROC 1
 .Os
 .Sh NAME
@@ -40,6 +40,11 @@ Print usage information and exit.
 .El
 .Sh COMPATIBILITY
 This program is intended to be compatible with nproc as found in GNU coreutils.
+.Sh BUGS
+If HyperThreading is enabled in BIOS and disabled in the kernel, the
+.Fl -all
+option on Linux will still report all possible CPU threads.
+On FreeBSD only active threads will be reported.
 .Sh SEE ALSO
 .Xr cpuset 1
 .Sh HISTORY
diff --git a/bin/nproc/nproc.c b/bin/nproc/nproc.c
index 9037c74dbfff..c2ab75826ce1 100644
--- a/bin/nproc/nproc.c
+++ b/bin/nproc/nproc.c
@@ -110,7 +110,7 @@ main(int argc, char *argv[])
 		usage();
 
 	if (all_flag) {
-		cpus = sysconf(_SC_NPROCESSORS_ONLN);
+		cpus = sysconf(_SC_NPROCESSORS_CONF);
 		if (cpus == -1)
 			err(1, "sysconf");
 	} else {