diff --git a/tools/git_sync_cl_chain.py b/tools/git_sync_cl_chain.py
index 97dcfb7..63c656d 100755
--- a/tools/git_sync_cl_chain.py
+++ b/tools/git_sync_cl_chain.py
@@ -70,7 +70,7 @@
       return
 
     stack = []
-    while True:
+    while current_branch:
       stack.append(current_branch)
       if current_branch.upstream is None or current_branch.upstream == 'master':
         break