diff --git a/hgext/transplant.py b/hgext/transplant.py
--- a/hgext/transplant.py
+++ b/hgext/transplant.py
@@ -246,6 +246,15 @@ class transplanter(object):
             m = match.exact(repo.root, '', files)
 
         n = repo.commit(message, user, date, extra=extra, match=m)
+        if not n:
+            # Crash here to prevent an unclear crash later, in
+            # transplants.write().  This can happen if patch.patch()
+            # does nothing but claims success or if repo.status() fails
+            # to report changes done by patch.patch().  These both
+            # appear to be bugs in other parts of Mercurial, but dying
+            # here, as soon as we can detect the problem, is preferable
+            # to silently dropping changesets on the floor.
+            raise RuntimeError('nothing committed after transplant')
         if not merge:
             self.transplants.set(n, node)