diff --git a/project.py b/project.py
index 1b0769a..65fefd9 100644
--- a/project.py
+++ b/project.py
@@ -1670,8 +1670,10 @@
     if GitCommand(self, cmd).Wait() != 0:
       raise GitError('%s rebase %s ' % (self.name, upstream))
 
-  def _FastForward(self, head):
+  def _FastForward(self, head, ffonly=False):
     cmd = ['merge', head]
+    if ffonly:
+      cmd.append("--ff-only")
     if GitCommand(self, cmd).Wait() != 0:
       raise GitError('%s merge %s ' % (self.name, head))