diff --git a/datajoint/settings.py b/datajoint/settings.py
index 7977053a3..022ce44b0 100644
--- a/datajoint/settings.py
+++ b/datajoint/settings.py
@@ -39,6 +39,8 @@ def __getitem__(self, key):
         return self._conf[key]
 
     def __setitem__(self, key, value):
+        if isinstance(value, collections.Mapping):
+            raise ValueError("Nested settings are not supported!")
         if validators[key](value):
             self._conf[key] = value
         else:
diff --git a/tests/test_settings.py b/tests/test_settings.py
index 988c19b3f..9dadcb43a 100644
--- a/tests/test_settings.py
+++ b/tests/test_settings.py
@@ -2,21 +2,9 @@
 
 __author__ = 'Fabian Sinz'
 
-from nose.tools import assert_true, assert_raises, assert_equal
+from nose.tools import assert_true, assert_raises, assert_equal, raises
 import datajoint as dj
 
-def nested_dict_compare(d1, d2):
-    for k, v in d1.items():
-        if k not in d2:
-            return False
-        else:
-            if isinstance(v, dict):
-                tmp = nested_dict_compare(v, d2[k])
-                if not tmp: return False
-            else:
-                if not v == d2[k]: return False
-    else:
-        return True
 
 def test_load_save():
     old = dj.config['config.file']
@@ -24,9 +12,16 @@ def test_load_save():
     dj.config.save()
     conf = dj.Config()
     conf.load('tmp.json')
-    assert_true(nested_dict_compare(conf, dj.config), 'Two config files do not match.')
+    assert_true(conf == dj.config, 'Two config files do not match.')
     dj.config['config.file'] = old
     os.remove('tmp.json')
 
+@raises(ValueError)
+def test_nested_check():
+    dummy = {'dummy.testval': {'notallowed': 2}}
+    dj.config.update(dummy)
 
+@raises(ValueError)
+def test_nested_check2():
+    dj.config['dummy'] = {'dummy2':2}