diff --git a/Documentation/git-am.adoc b/Documentation/git-am.adoc
index 221070de48..264d21a7de 100644
--- a/Documentation/git-am.adoc
+++ b/Documentation/git-am.adoc
@@ -161,6 +161,13 @@ Valid <action> for the `--whitespace` option are:
 	commit creation as the committer date. This allows the
 	user to lie about the committer date by using the same
 	value as the author date.
++
+WARNING: The history walking machinery assumes that commits have
+non-decreasing commit timestamps. You should consider if you really need
+to use this option. Then you should only use this option to override the
+committer date when applying commits on top of a base which commit is
+older (in terms of the commit date) than the oldest patch you are
+applying.
 
 --ignore-date::
 	By default the command records the date from the e-mail
diff --git a/Documentation/git-rebase.adoc b/Documentation/git-rebase.adoc
index 956d3048f5..0f808c82b2 100644
--- a/Documentation/git-rebase.adoc
+++ b/Documentation/git-rebase.adoc
@@ -507,6 +507,13 @@ See also INCOMPATIBLE OPTIONS below.
 	Instead of using the current time as the committer date, use
 	the author date of the commit being rebased as the committer
 	date. This option implies `--force-rebase`.
++
+WARNING: The history walking machinery assumes that commits have
+non-decreasing commit timestamps. You should consider if you really need
+to use this option. Then you should only use this option to override the
+committer date when rebasing commits on top of a base which commit is
+older (in terms of the commit date) than the oldest commit you are
+applying (in terms of the author date).
 
 --ignore-date::
 --reset-author-date::