diff --git a/sbin/dumpon/dumpon.8 b/sbin/dumpon/dumpon.8
index 096cbde246d0..0c478e098344 100644
--- a/sbin/dumpon/dumpon.8
+++ b/sbin/dumpon/dumpon.8
@@ -58,7 +58,7 @@ variable in the boot time configuration file
 .Pp
 For most systems the size of the specified dump device must be at
 least the size of physical memory.
-Even though an additional header is added to the dump, the BIOS for a
+Even though an additional 64 kB header is added to the dump, the BIOS for a
 platform typically holds back some memory, so it is not usually
 necessary to size the dump device larger than the actual amount of RAM
 available in the machine.