diff --git a/pyramid/config/settings.py b/pyramid/config/settings.py
index 26eb48951b..52b30db81d 100644
--- a/pyramid/config/settings.py
+++ b/pyramid/config/settings.py
@@ -56,6 +56,7 @@ def Settings(d=None, _environ_=os.environ, **kw):
     keyword args)."""
     if d is None:
         d = {}
+    d = dict(d)
     d.update(**kw)
 
     eget = _environ_.get
diff --git a/pyramid/tests/test_config/test_settings.py b/pyramid/tests/test_config/test_settings.py
index d6fb8de67b..202629358e 100644
--- a/pyramid/tests/test_config/test_settings.py
+++ b/pyramid/tests/test_config/test_settings.py
@@ -12,12 +12,12 @@ def test__set_settings_as_None(self):
         settings = config._set_settings(None)
         self.assertTrue(settings)
 
-    def test__set_settings_uses_original_dict(self):
+    def test__set_settings_does_not_uses_original_dict(self):
         config = self._makeOne()
         dummy = {}
         result = config._set_settings(dummy)
-        self.assertTrue(dummy is result)
-        self.assertEqual(dummy['pyramid.debug_all'], False)
+        self.assertTrue(dummy is not result)
+        self.assertNotIn('pyramid.debug_all', dummy)
 
     def test__set_settings_as_dictwithvalues(self):
         config = self._makeOne()