diff --git a/monasca_common/tests/validation/test_metric_validation.py b/monasca_common/tests/validation/test_metric_validation.py
index 7ee87203..29595cc4 100644
--- a/monasca_common/tests/validation/test_metric_validation.py
+++ b/monasca_common/tests/validation/test_metric_validation.py
@@ -24,7 +24,7 @@ invalid_name_chars = " <>={}(),\"\\\\;&"
 
 # a few valid characters to test
 valid_dimension_chars = " .'_-"
-invalid_dimension_chars = "<>={}(),\"\\\\;&"
+invalid_dimension_chars = "<>={},\"\\\\;&"
 
 
 class TestMetricValidation(base.BaseTestCase):
@@ -182,7 +182,7 @@ class TestMetricValidation(base.BaseTestCase):
 
     def test_invalid_dimension_key_restricted_characters(self):
         metric = {"name": "test_metric_name",
-                  "dimensions": {'A': 'B', 'B': 'C', '(D)': 'E'},
+                  "dimensions": {'A': 'B', 'B': 'C', 'D=': 'E'},
                   "timestamp": 1405630174123,
                   "value": 5}
         self.assertRaisesRegex(
diff --git a/monasca_common/validation/metrics.py b/monasca_common/validation/metrics.py
index 1b67da93..c7da5bb9 100644
--- a/monasca_common/validation/metrics.py
+++ b/monasca_common/validation/metrics.py
@@ -30,9 +30,9 @@ VALUE_META_MAX_NUMBER = 16
 VALUE_META_VALUE_MAX_LENGTH = 2048
 VALUE_META_NAME_MAX_LENGTH = 255
 
-INVALID_CHARS = "<>={}(),\"\\\\;&"
+INVALID_CHARS = "<>={},\"\\\\;&"
 RESTRICTED_DIMENSION_CHARS = re.compile('[' + INVALID_CHARS + ']')
-RESTRICTED_NAME_CHARS = re.compile('[' + INVALID_CHARS + ' ' + ']')
+RESTRICTED_NAME_CHARS = re.compile('[' + INVALID_CHARS + '() ' + ']')
 
 NUMERIC_VALUES = [int, float]
 if six.PY2:
@@ -42,6 +42,7 @@ if six.PY2:
 
 NUMERIC_VALUES = tuple(NUMERIC_VALUES)  # convert to tuple for instance call
 
+
 class InvalidMetricName(Exception):
     pass