diff --git a/toscaparser/unsupportedtype.py b/toscaparser/unsupportedtype.py
index 0d2f1d6c..a0c11f0f 100644
--- a/toscaparser/unsupportedtype.py
+++ b/toscaparser/unsupportedtype.py
@@ -20,6 +20,18 @@ log = logging.getLogger('tosca')
 
 class UnsupportedType(object):
 
+    """Note: TOSCA spec version related
+
+    The tosca.nodes.Storage.ObjectStorage and tosca.nodes.Storage.BlockStorage
+    used here as un_supported_types are part of the name changes in TOSCA spec
+    version 1.1. The original name as specified in version 1.0 are,
+    tosca.nodes.BlockStorage and tosca.nodes.ObjectStorage which are supported
+    by the tosca-parser. Since there are little overlapping in version support
+    currently in the tosca-parser, the names tosca.nodes.Storage.ObjectStorage
+    and tosca.nodes.Storage.BlockStorage are used here to demonstrate the usage
+    of un_supported_types. As tosca-parser move to provide support for version
+    1.1 and higher, they will be removed.
+    """
     un_supported_types = ['tosca.test.invalidtype',
                           'tosca.nodes.Storage.ObjectStorage',
                           'tosca.nodes.Storage.BlockStorage']