diff --git a/ceilometer/collector/meter.py b/ceilometer/collector/meter.py
index 77074cf0..4b6d8a7c 100644
--- a/ceilometer/collector/meter.py
+++ b/ceilometer/collector/meter.py
@@ -48,6 +48,12 @@ def recursive_keypairs(d):
         if isinstance(value, dict):
             for subname, subvalue in recursive_keypairs(value):
                 yield ('%s:%s' % (name, subname), subvalue)
+        elif isinstance(value, (tuple, list)):
+            # When doing a pair of JSON encode/decode operations to the tuple,
+            # the tuple would become list. So we have to generate the value as
+            # list here.
+            yield name, list(map(lambda x: unicode(x).encode('utf-8'),
+                                 value))
         else:
             yield name, value
 
diff --git a/ceilometer/compute/pollsters.py b/ceilometer/compute/pollsters.py
index f74a3a0e..d877dae8 100644
--- a/ceilometer/compute/pollsters.py
+++ b/ceilometer/compute/pollsters.py
@@ -210,7 +210,7 @@ class NetPollster(plugin.ComputePollster):
         resource_metadata = dict(zip(metadata._fields, metadata))
         resource_metadata['instance_id'] = instance.id
         resource_metadata['instance_type'] = \
-            instance.flavor['id'] if instance.flavor else None,
+            instance.flavor['id'] if instance.flavor else None
 
         return counter.Counter(
             name=name,
diff --git a/tests/collector/test_meter.py b/tests/collector/test_meter.py
index 2831e5f4..a1314062 100644
--- a/tests/collector/test_meter.py
+++ b/tests/collector/test_meter.py
@@ -20,6 +20,7 @@
 
 from ceilometer.collector import meter
 from ceilometer import counter
+from ceilometer.openstack.common import jsonutils
 
 
 def test_compute_signature_change_key():
@@ -99,6 +100,20 @@ def test_verify_signature_nested():
     assert meter.verify_signature(data, 'not-so-secret')
 
 
+def test_verify_signature_nested_json():
+    data = {'a': 'A',
+            'b': 'B',
+            'nested': {'a': 'A',
+                       'b': 'B',
+                       'c': ('c',),
+                       'd': ['d']
+                       },
+            }
+    data['message_signature'] = meter.compute_signature(data, 'not-so-secret')
+    jsondata = jsonutils.loads(jsonutils.dumps(data))
+    assert meter.verify_signature(jsondata, 'not-so-secret')
+
+
 TEST_COUNTER = counter.Counter(name='name',
                                type='typ',
                                unit='',