diff --git a/man/man8/zfs.8 b/man/man8/zfs.8
index 15ec8477e62f..e485211fc3fa 100644
--- a/man/man8/zfs.8
+++ b/man/man8/zfs.8
@@ -353,6 +353,8 @@ If needed, \fBZFS\fR file systems can also be managed with traditional tools (\f
 .SS "Deduplication"
 .LP
 Deduplication is the process for removing redundant data at the block-level, reducing the total amount of data stored. If a file system has the \fBdedup\fR property enabled, duplicate data blocks are removed synchronously.  The result is that only unique data is stored and common components are shared among files.
+.sp
+\fBWARNING\fR: Please don't enable this unless you know \fUexactly\fR what you're doing! It can be very dangerous and can result in pool loss if you don't have enough memory.
 .SS "Native Properties"
 .LP
 Properties are divided into two types, native properties and user-defined (or "user") properties. Native properties either export internal statistics or control \fBZFS\fR behavior. In addition, native properties are either editable or read-only. User properties have no effect on \fBZFS\fR behavior, but you can use them to annotate datasets in a way that is meaningful in your environment. For more information about user properties, see the "User Properties" section, below.