diff --git a/presubmit_support.py b/presubmit_support.py
index 85b3a3f70..0efaca1c8 100755
--- a/presubmit_support.py
+++ b/presubmit_support.py
@@ -690,6 +690,9 @@ class Change(object):
     self._description_without_tags = (
         '\n'.join(description_without_tags).rstrip())
 
+    assert all(
+        (isinstance(f, (list, tuple)) and len(f) == 2) for f in files), files
+
     self._affected_files = [
         self._AFFECTED_FILES(info[1], info[0].strip(), self._local_root)
         for info in files
diff --git a/tests/presubmit_unittest.py b/tests/presubmit_unittest.py
index 055e8b6fc..0c066d17d 100755
--- a/tests/presubmit_unittest.py
+++ b/tests/presubmit_unittest.py
@@ -351,6 +351,20 @@ class PresubmitUnittest(PresubmitTestsBase):
     self.assertEquals(rhs_lines[13][1], 49)
     self.assertEquals(rhs_lines[13][2], 'this is line number 48.1')
 
+  def testInvalidChange(self):
+    try:
+      presubmit.SvnChange(
+          'mychange',
+          'description',
+          self.fake_root_dir,
+          ['foo/blat.cc', 'bar'],
+          0,
+          0,
+          None)
+      self.fail()
+    except AssertionError:
+      pass
+
   def testExecPresubmitScript(self):
     description_lines = ('Hello there',
                          'this is a change',
@@ -770,7 +784,7 @@ def CheckChangeOnCommit(input_api, output_api):
     self.mox.StubOutWithMock(presubmit, 'ParseFiles')
     presubmit.scm.determine_scm(self.fake_root_dir).AndReturn(None)
     presubmit.ParseFiles(['random_file.txt'], None
-        ).AndReturn(['random_file.txt'])
+        ).AndReturn([('M', 'random_file.txt')])
     output = self.mox.CreateMock(presubmit.PresubmitOutput)
     output.should_continue().AndReturn(False)