diff --git a/keystoneclient/tests/v3/test_credentials.py b/keystoneclient/tests/v3/test_credentials.py
index 50b4a9316..be9903393 100644
--- a/keystoneclient/tests/v3/test_credentials.py
+++ b/keystoneclient/tests/v3/test_credentials.py
@@ -28,8 +28,28 @@ class CredentialTests(utils.TestCase, utils.CrudTests):
 
     def new_ref(self, **kwargs):
         kwargs = super(CredentialTests, self).new_ref(**kwargs)
-        kwargs.setdefault('data', uuid.uuid4().hex)
+        kwargs.setdefault('blob', uuid.uuid4().hex)
         kwargs.setdefault('project_id', uuid.uuid4().hex)
         kwargs.setdefault('type', uuid.uuid4().hex)
         kwargs.setdefault('user_id', uuid.uuid4().hex)
         return kwargs
+
+    @staticmethod
+    def _ref_data_not_blob(ref):
+        ret_ref = ref.copy()
+        ret_ref['data'] = ref['blob']
+        del ret_ref['blob']
+        return ret_ref
+
+    def test_create_data_not_blob(self):
+        # Test create operation with previous, deprecated "data" argument,
+        # which should be translated into "blob" at the API call level
+        req_ref = self.new_ref()
+        api_ref = self._ref_data_not_blob(req_ref)
+        self.test_create(api_ref, req_ref)
+
+    def test_update_data_not_blob(self):
+        # Likewise test update operation with data instead of blob argument
+        req_ref = self.new_ref()
+        api_ref = self._ref_data_not_blob(req_ref)
+        self.test_update(api_ref, req_ref)
diff --git a/keystoneclient/tests/v3/utils.py b/keystoneclient/tests/v3/utils.py
index 182e947c3..3ec35b1e9 100644
--- a/keystoneclient/tests/v3/utils.py
+++ b/keystoneclient/tests/v3/utils.py
@@ -261,12 +261,16 @@ class CrudTests(object):
             self.assertQueryStringIs({})
 
     @httpretty.activate
-    def test_update(self, ref=None):
+    def test_update(self, ref=None, req_ref=None):
         ref = ref or self.new_ref()
 
         self.stub_entity(httpretty.PATCH, id=ref['id'], entity=ref)
 
-        req_ref = ref.copy()
+        # req_ref argument allows you to specify a different
+        # signature for the request when the manager does some
+        # conversion before doing the request (e.g converting
+        # from datetime object to timestamp string)
+        req_ref = (req_ref or ref).copy()
         req_ref.pop('id')
 
         returned = self.manager.update(ref['id'], **parameterize(req_ref))
diff --git a/keystoneclient/v3/credentials.py b/keystoneclient/v3/credentials.py
index 6403d8d17..35fab1c9c 100644
--- a/keystoneclient/v3/credentials.py
+++ b/keystoneclient/v3/credentials.py
@@ -33,11 +33,25 @@ class CredentialManager(base.CrudManager):
     collection_key = 'credentials'
     key = 'credential'
 
-    def create(self, user, type, data, project=None):
+    def _get_data_blob(self, blob, data):
+        # Ref bug #1259461, the <= 0.4.1 keystoneclient calling convention was
+        # to pass "data", but the underlying API expects "blob", so
+        # support both in the python API for backwards compatibility
+        if blob is not None:
+            return blob
+        elif data is not None:
+            # FIXME(shardy): Passing data is deprecated. Provide an
+            # appropriate warning.
+            return data
+        else:
+            raise ValueError(
+                "Credential requires blob to be specified")
+
+    def create(self, user, type, blob=None, data=None, project=None):
         return super(CredentialManager, self).create(
             user_id=base.getid(user),
             type=type,
-            data=data,
+            blob=self._get_data_blob(blob, data),
             project_id=base.getid(project))
 
     def get(self, credential):
@@ -47,12 +61,13 @@ class CredentialManager(base.CrudManager):
     def list(self):
         return super(CredentialManager, self).list()
 
-    def update(self, credential, user, type=None, data=None, project=None):
+    def update(self, credential, user, type=None, blob=None, data=None,
+               project=None):
         return super(CredentialManager, self).update(
             credential_id=base.getid(credential),
             user_id=base.getid(user),
             type=type,
-            data=data,
+            blob=self._get_data_blob(blob, data),
             project_id=base.getid(project))
 
     def delete(self, credential):