--- a/hgsubversion/editor.py
+++ b/hgsubversion/editor.py
@@ -356,7 +356,19 @@ class HgEditor(svnwrap.Editor):
             try:
                 if not self.meta.is_path_valid(self.current.file):
                     return
-                handler(window)
+                try:
+                    handler(window)
+                except AssertionError, e: # pragma: no cover
+                    # Enhance the exception message
+                    msg, others = e.args[0], e.args[1:]
+
+                    if msg:
+                        msg += '\n'
+
+                    msg += _TXDELT_WINDOW_HANDLER_FAILURE_MSG
+                    e.args = (msg,) + others
+                    raise e
+
                 # window being None means commit this file
                 if not window:
                     self.current.files[self.current.file] = target.getvalue()
@@ -369,3 +381,13 @@ class HgEditor(svnwrap.Editor):
                 self._exception_info = sys.exc_info()
                 raise
         return txdelt_window
+
+_TXDELT_WINDOW_HANDLER_FAILURE_MSG = (
+    "Your SVN repository may not be supplying correct replay deltas."
+    " It is strongly"
+    "\nadvised that you repull the entire SVN repository using"
+    " hg pull --stupid."
+    "\nAlternatively, re-pull just this revision using --stupid and verify"
+    " that the"
+    "\nchangeset is correct."
+)

--- a/hgsubversion/stupid.py
+++ b/hgsubversion/stupid.py
@@ -22,7 +22,7 @@ import util
 #  a
 #  a
 # +a
-# 
+#
 # Property changes on: a
 # ___________________________________________________________________
 # Added: svn:executable
@@ -239,11 +239,16 @@ def patchrepo(ui, meta, parentctx, patch
     try:
         touched = set()
         backend = svnbackend(ui, meta.repo, parentctx, store)
-        ret = patch.patchbackend(ui, backend, patchfp, 0, touched)
-        if ret < 0:
-            raise BadPatchApply('patching failed')
-        if ret > 0:
-            raise BadPatchApply('patching succeeded with fuzz')
+
+        try:
+            ret = patch.patchbackend(ui, backend, patchfp, 0, touched)
+            if ret < 0:
+                raise BadPatchApply('patching failed')
+            if ret > 0:
+                raise BadPatchApply('patching succeeded with fuzz')
+        except patch.PatchError, e:
+            raise BadPatchApply(str(e))
+
         files = {}
         for f in touched:
             try:

--- a/tests/run.py
+++ b/tests/run.py
@@ -20,6 +20,7 @@ def tests():
     import test_fetch_truncated
     import test_hooks
     import test_pull
+    import test_pull_fallback
     import test_push_command
     import test_push_renames
     import test_push_dirs

new file mode 100644
--- /dev/null
+++ b/tests/test_pull_fallback.py
@@ -0,0 +1,106 @@
+import test_util
+
+import re
+import mercurial
+from mercurial import commands
+from hgsubversion import stupid
+from hgsubversion import svnwrap
+from hgsubversion import wrappers
+
+class TestPullFallback(test_util.TestBase):
+    def setUp(self):
+        super(TestPullFallback, self).setUp()
+
+    def _loadupdate(self, fixture_name, *args, **kwargs):
+        kwargs = kwargs.copy()
+        kwargs.update(noupdate=False)
+        repo, repo_path = self.load_and_fetch(fixture_name, *args, **kwargs)
+        return repo, repo_path
+
+    def test_stupid_fallback_to_stupid_fullrevs(self):
+        return
+        to_patch = {
+            'mercurial.patch.patchbackend': _patchbackend_raise,
+            'stupid.diff_branchrev': stupid.diff_branchrev,
+            'stupid.fetch_branchrev': stupid.fetch_branchrev,
+        }
+
+        expected_calls = {
+            'mercurial.patch.patchbackend': 1,
+            'stupid.diff_branchrev': 1,
+            'stupid.fetch_branchrev': 1,
+        }
+
+        repo, repo_path = self._loadupdate(
+            'single_rev.svndump', stupid=True)
+
+        # Passing stupid=True doesn't seem to be working - force it
+        repo.ui.setconfig('hgsubversion', 'stupid', "true")
+        state = repo.parents()
+
+        calls, replaced = _monkey_patch(to_patch)
+
+        try:
+            self.add_svn_rev(repo_path, {'trunk/alpha': 'Changed'})
+            commands.pull(self.repo.ui, repo, update=True)
+            self.failIfEqual(state, repo.parents())
+            self.assertTrue('tip' in repo[None].tags())
+            self.assertEqual(expected_calls, calls)
+
+        finally:
+            _monkey_unpatch(replaced)
+
+def _monkey_patch(to_patch, start=None):
+    if start is None:
+        import sys
+        start = sys.modules[__name__]
+
+    calls = {}
+    replaced = {}
+
+    for path, replacement in to_patch.iteritems():
+        obj = start
+        owner, attr = path.rsplit('.', 1)
+
+        for a in owner.split('.', -1):
+            obj = getattr(obj, a)
+
+        replaced[path] = getattr(obj, attr)
+        calls[path] = 0
+
+        def outer(path=path, calls=calls, replacement=replacement):
+            def wrapper(*p, **kw):
+                calls[path] += 1
+                return replacement(*p, **kw)
+
+            return wrapper
+
+        setattr(obj, attr, outer())
+
+    return calls, replaced
+
+def _monkey_unpatch(to_patch, start=None):
+    if start is None:
+        import sys
+        start = sys.modules[__name__]
+
+    replaced = {}
+
+    for path, replacement in to_patch.iteritems():
+        obj = start
+        owner, attr = path.rsplit('.', 1)
+
+        for a in owner.split('.', -1):
+            obj = getattr(obj, a)
+
+        replaced[path] = getattr(obj, attr)
+        setattr(obj, attr, replacement)
+
+    return replaced
+
+def _patchbackend_raise(*p, **kw):
+    raise mercurial.patch.PatchError("patch failed")
+
+def suite():
+    import unittest, sys
+    return unittest.findTestCases(sys.modules[__name__])