diff --git a/Documentation/git-index-pack.txt b/Documentation/git-index-pack.txt
index ac74d058e0..af0c26232c 100644
--- a/Documentation/git-index-pack.txt
+++ b/Documentation/git-index-pack.txt
@@ -100,6 +100,8 @@ OPTIONS
 	value is set or outside a repository.
 +
 This option cannot be used with --stdin.
++
+include::object-format-disclaimer.txt[]
 
 NOTES
 -----
diff --git a/Documentation/git-init.txt b/Documentation/git-init.txt
index ddfe265da5..f35f70f13d 100644
--- a/Documentation/git-init.txt
+++ b/Documentation/git-init.txt
@@ -53,6 +53,8 @@ current working directory.
 
 Specify the given object format (hash algorithm) for the repository.  The valid
 values are 'sha1' and (if enabled) 'sha256'.  'sha1' is the default.
++
+include::object-format-disclaimer.txt[]
 
 --template=<template_directory>::
 
diff --git a/Documentation/git-show-index.txt b/Documentation/git-show-index.txt
index 39b1d8eaa1..e49318a5a0 100644
--- a/Documentation/git-show-index.txt
+++ b/Documentation/git-show-index.txt
@@ -44,6 +44,8 @@ OPTIONS
 	valid values are 'sha1' and (if enabled) 'sha256'.  The default is the
 	algorithm for the current repository (set by `extensions.objectFormat`), or
 	'sha1' if no value is set or outside a repository..
++
+include::object-format-disclaimer.txt[]
 
 GIT
 ---
diff --git a/Documentation/git.txt b/Documentation/git.txt
index 3e50065198..e0a2690ba2 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -497,7 +497,8 @@ double-quotes and respecting backslash escapes. E.g., the value
 	If this variable is set, the default hash algorithm for new
 	repositories will be set to this value. This value is currently
 	ignored when cloning; the setting of the remote repository
-	is used instead. The default is "sha1".
+	is used instead. The default is "sha1". THIS VARIABLE IS
+	EXPERIMENTAL! See `--object-format` in linkgit:git-init[1].
 
 Git Commits
 ~~~~~~~~~~~
diff --git a/Documentation/object-format-disclaimer.txt b/Documentation/object-format-disclaimer.txt
new file mode 100644
index 0000000000..4cb106f0d1
--- /dev/null
+++ b/Documentation/object-format-disclaimer.txt
@@ -0,0 +1,6 @@
+THIS OPTION IS EXPERIMENTAL! SHA-256 support is experimental and still
+in an early stage.  A SHA-256 repository will in general not be able to
+share work with "regular" SHA-1 repositories.  It should be assumed
+that, e.g., Git internal file formats in relation to SHA-256
+repositories may change in backwards-incompatible ways.  Only use
+`--object-format=sha256` for testing purposes.