diff --git a/etc/heat/templates/AWS_CloudWatch_Alarm.yaml b/etc/heat/templates/AWS_CloudWatch_Alarm.yaml
index e21e500d6..2e5f36625 100644
--- a/etc/heat/templates/AWS_CloudWatch_Alarm.yaml
+++ b/etc/heat/templates/AWS_CloudWatch_Alarm.yaml
@@ -43,6 +43,7 @@ Parameters:
    Default: ''
   Dimensions:
    Type: CommaDelimitedList
+   Default: ''
 
 Mappings:
   ComparisonOperatorMap:
diff --git a/heat/engine/parameters.py b/heat/engine/parameters.py
index 2118f8aff..76f108f89 100644
--- a/heat/engine/parameters.py
+++ b/heat/engine/parameters.py
@@ -335,6 +335,8 @@ class CommaDelimitedListParam(Parameter, collections.Sequence):
             return value
         try:
             if value is not None:
+                if value == '':
+                    return []
                 return value.split(',')
         except (KeyError, AttributeError) as err:
             message = _('Value must be a comma-delimited list string: %s')
diff --git a/heat/tests/test_parameters.py b/heat/tests/test_parameters.py
index ef0885563..8c0e6c209 100644
--- a/heat/tests/test_parameters.py
+++ b/heat/tests/test_parameters.py
@@ -251,10 +251,9 @@ class ParameterTest(testtools.TestCase):
         self.assertIn('wibble', six.text_type(err))
 
     def test_list_value_list_default_empty(self):
-        schema = {'Type': 'CommaDelimitedList'}
-        schema['Default'] = ''
+        schema = {'Type': 'CommaDelimitedList', 'Default': ''}
         p = self.new_parameter('p', schema)
-        self.assertEqual([''], p.value())
+        self.assertEqual([], p.value())
 
     def test_list_value_list_good(self):
         schema = {'Type': 'CommaDelimitedList',