diff --git a/Documentation/git-log.txt b/Documentation/git-log.txt
index 3726ca0d44..59c42c29d2 100644
--- a/Documentation/git-log.txt
+++ b/Documentation/git-log.txt
@@ -76,7 +76,8 @@ produced by `--stat`, etc.
 	(or the function name regex <funcname>) within the <file>.  You may
 	not give any pathspec limiters.  This is currently limited to
 	a walk starting from a single revision, i.e., you may only
-	give zero or one positive revision arguments.
+	give zero or one positive revision arguments, and
+	<start> and <end> (or <funcname>) must exist in the starting revision.
 	You can specify this option more than once. Implies `--patch`.
 	Patch output can be suppressed using `--no-patch`, but other diff formats
 	(namely `--raw`, `--numstat`, `--shortstat`, `--dirstat`, `--summary`,
diff --git a/Documentation/gitk.txt b/Documentation/gitk.txt
index c487af5b74..c653ebb6a8 100644
--- a/Documentation/gitk.txt
+++ b/Documentation/gitk.txt
@@ -105,7 +105,8 @@ linkgit:git-rev-list[1] for a complete list.
 	(or the function name regex <funcname>) within the <file>.  You may
 	not give any pathspec limiters.  This is currently limited to
 	a walk starting from a single revision, i.e., you may only
-	give zero or one positive revision arguments.
+	give zero or one positive revision arguments, and
+	<start> and <end> (or <funcname>) must exist in the starting revision.
 	You can specify this option more than once. Implies `--patch`.
 	Patch output can be suppressed using `--no-patch`, but other diff formats
 	(namely `--raw`, `--numstat`, `--shortstat`, `--dirstat`, `--summary`,