diff --git a/project.py b/project.py
index 8212e0c..4076bc5 100755
--- a/project.py
+++ b/project.py
@@ -1697,7 +1697,7 @@
 
 # Branch Management ##
 
-  def StartBranch(self, name, branch_merge=''):
+  def StartBranch(self, name, branch_merge='', revision=None):
     """Create a new branch off the manifest's revision.
     """
     if not branch_merge:
@@ -1718,7 +1718,11 @@
     branch.merge = branch_merge
     if not branch.merge.startswith('refs/') and not ID_RE.match(branch_merge):
       branch.merge = R_HEADS + branch_merge
-    revid = self.GetRevisionId(all_refs)
+
+    if revision is None:
+      revid = self.GetRevisionId(all_refs)
+    else:
+      revid = self.work_git.rev_parse(revision)
 
     if head.startswith(R_HEADS):
       try: