diff --git a/Lib/doctest.py b/Lib/doctest.py
index 3a8496f..2aa7408 100644
--- a/Lib/doctest.py
+++ b/Lib/doctest.py
@@ -1019,7 +1019,7 @@
                                      "must be strings, functions, methods, "
                                      "classes, or modules: %r" %
                                      (type(val),))
-                valname = '%s.%s' % (name, valname)
+                valname = '%s.__test__.%s' % (name, valname)
                 self._find(tests, val, valname, module, source_lines,
                            globs, seen)
 
diff --git a/Lib/test/test_doctest.py b/Lib/test/test_doctest.py
index 2b287ed..d60738b 100644
--- a/Lib/test/test_doctest.py
+++ b/Lib/test/test_doctest.py
@@ -467,8 +467,8 @@
      1  some_module.SampleClass.a_staticmethod
      1  some_module.SampleClass.double
      1  some_module.SampleClass.get
-     1  some_module.c
-     2  some_module.d
+     1  some_module.__test__.c
+     2  some_module.__test__.d
      1  some_module.sample_func
 
 Duplicate Removal
diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
index ca6eebd..109af73 100644
--- a/Lib/test/test_generators.py
+++ b/Lib/test/test_generators.py
@@ -654,14 +654,14 @@
 ...     yield 1
 Traceback (most recent call last):
   ..
-SyntaxError: 'return' with argument inside generator (<doctest test.test_generators.syntax[0]>, line 2)
+SyntaxError: 'return' with argument inside generator (<doctest test.test_generators.__test__.syntax[0]>, line 2)
 
 >>> def f():
 ...     yield 1
 ...     return 22
 Traceback (most recent call last):
   ..
-SyntaxError: 'return' with argument inside generator (<doctest test.test_generators.syntax[1]>, line 3)
+SyntaxError: 'return' with argument inside generator (<doctest test.test_generators.__test__.syntax[1]>, line 3)
 
 "return None" is not the same as "return" in a generator:
 
@@ -670,7 +670,7 @@
 ...     return None
 Traceback (most recent call last):
   ..
-SyntaxError: 'return' with argument inside generator (<doctest test.test_generators.syntax[2]>, line 3)
+SyntaxError: 'return' with argument inside generator (<doctest test.test_generators.__test__.syntax[2]>, line 3)
 
 This one is fine:
 
@@ -685,7 +685,7 @@
 ...         pass
 Traceback (most recent call last):
   ..
-SyntaxError: 'yield' not allowed in a 'try' block with a 'finally' clause (<doctest test.test_generators.syntax[4]>, line 3)
+SyntaxError: 'yield' not allowed in a 'try' block with a 'finally' clause (<doctest test.test_generators.__test__.syntax[4]>, line 3)
 
 >>> def f():
 ...     try:
@@ -699,7 +699,7 @@
 ...         pass
 Traceback (most recent call last):
   ...
-SyntaxError: 'yield' not allowed in a 'try' block with a 'finally' clause (<doctest test.test_generators.syntax[5]>, line 6)
+SyntaxError: 'yield' not allowed in a 'try' block with a 'finally' clause (<doctest test.test_generators.__test__.syntax[5]>, line 6)
 
 But this is fine:
 
@@ -805,7 +805,7 @@
 ...     if 0:
 ...         yield 2             # because it's a generator
 Traceback (most recent call last):
-SyntaxError: 'return' with argument inside generator (<doctest test.test_generators.syntax[22]>, line 8)
+SyntaxError: 'return' with argument inside generator (<doctest test.test_generators.__test__.syntax[22]>, line 8)
 
 This one caused a crash (see SF bug 567538):