1 files changed, 3 insertions, 0 deletions
diff --git a/b4/diff.py b/b4/diff.py
index 81e015a..10f3159 100644
--- a/b4/diff.py
+++ b/b4/diff.py
@@ -101,6 +101,9 @@ def diff_mboxes(cmdargs):
         lmbx = b4.LoreMailbox()
         for key, msg in mbx.items():
             lmbx.add_message(msg)
+        if len(lmbx.series) < 1:
+            logger.critical('No valid patches found in %s', mboxfile)
+            sys.exit(1)
         if len(lmbx.series) > 1:
             logger.critical('More than one series version in %s, will use latest', mboxfile)