diff --git a/Documentation/error-messages.txt b/Documentation/error-messages.txt
index 2f0a8f2c95..e84e6b3107 100644
--- a/Documentation/error-messages.txt
+++ b/Documentation/error-messages.txt
@@ -14,6 +14,7 @@ Error Messages
 * link:error-invalid-changeid.html[invalid Change-Id line format in commit message]
 * link:error-missing-changeid.html[missing Change-Id in commit message]
 * link:error-multiple-changeid-lines.html[multiple Change-Id lines in commit message]
+* link:error-no-common-ancestry.html[no common ancestry]
 * link:error-no-new-changes.html[no new changes]
 * link:error-not-a-gerrit-project.html[not a Gerrit project]
 * link:error-not-valid-ref.html[not valid ref]
diff --git a/Documentation/error-no-common-ancestry.txt b/Documentation/error-no-common-ancestry.txt
new file mode 100644
index 0000000000..615da712c5
--- /dev/null
+++ b/Documentation/error-no-common-ancestry.txt
@@ -0,0 +1,20 @@
+no common ancestry
+==================
+
+With this error message Gerrit rejects to push a commit for code
+review if the pushed commit and the commit at the tip of the target
+branch do not have a common ancestry.
+
+This means that your local development history and the development
+history of the branch to which the push is done are completely
+independent (they have completely independent commit graphs).
+
+This error usually occurs if you do a change in one project and then
+you accidentally push the commit to another project for code review.
+To fix the problem you should check your push specification and
+verify that you are pushing the commit to the correct project.
+
+
+GERRIT
+------
+Part of link:error-messages.html[Gerrit Error Messages]