diff --git a/Lib/doctest.py b/Lib/doctest.py
index 726517e..a9357b5 100644
--- a/Lib/doctest.py
+++ b/Lib/doctest.py
@@ -1328,7 +1328,8 @@
         m = self.__LINECACHE_FILENAME_RE.match(filename)
         if m and m.group('name') == self.test.name:
             example = self.test.examples[int(m.group('examplenum'))]
-            return example.source.splitlines(True)
+            source = example.source.encode('ascii', 'backslashreplace')
+            return source.splitlines(True)
         else:
             return self.save_linecache_getlines(filename, module_globals)