diff --git a/docs/manifest-format.txt b/docs/manifest-format.txt
index 0bf09f6..f4629a5 100644
--- a/docs/manifest-format.txt
+++ b/docs/manifest-format.txt
@@ -56,6 +56,7 @@
     <!ATTLIST project sync-c   CDATA #IMPLIED>
     <!ATTLIST project sync-s   CDATA #IMPLIED>
     <!ATTLIST project upstream CDATA #IMPLIED>
+    <!ATTLIST project clone-depth CDATA #IMPLIED>
 
     <!ELEMENT annotation (EMPTY)>
     <!ATTLIST annotation name  CDATA #REQUIRED>
@@ -222,6 +223,10 @@
 can be found.  Used when syncing a revision locked manifest in
 -c mode to avoid having to sync the entire ref space.
 
+Attribute `clone-depth`: Set the depth to use when fetching this
+project.  If specified, this value will override any value given
+to repo init with the --depth option on the command line.
+
 Element annotation
 ------------------