diff -r 07ee5004656a Lib/dbm/__init__.py
--- a/Lib/dbm/__init__.py	Mon Mar 14 12:37:25 2011 -0400
+++ b/Lib/dbm/__init__.py	Mon Mar 14 13:26:34 2011 -0400
@@ -67,10 +67,10 @@
         if not _defaultmod:
             raise ImportError("no dbm clone found; tried %s" % _names)
 
-    # guess the type of an existing database
-    result = whichdb(file)
+    # guess the type of an existing database, if not creating a new one
+    result = whichdb(file) if 'n' not in flag else None
     if result is None:
-        # db doesn't exist
+        # db doesn't exist or 'n' flag was specified to create a new db
         if 'c' in flag or 'n' in flag:
             # file doesn't exist and the new flag was used so use default type
             mod = _defaultmod
diff -r 07ee5004656a Lib/test/test_dbm.py
--- a/Lib/test/test_dbm.py	Mon Mar 14 12:37:25 2011 -0400
+++ b/Lib/test/test_dbm.py	Mon Mar 14 13:26:34 2011 -0400
@@ -70,6 +70,14 @@
         self.read_helper(f)
         f.close()
 
+    def test_anydbm_creation_n_file_exists_with_invalid_contents(self):
+        with open(_fname, "w") as w:
+            pass # create an empty file
+
+        f = dbm.open(_fname, 'n')
+        self.addCleanup(f.close)
+        self.assertEqual(len(f), 0)
+
     def test_anydbm_modification(self):
         self.init_db()
         f = dbm.open(_fname, 'c')