diff --git a/heatclient/common/http.py b/heatclient/common/http.py
index 576e3642..16d1bf62 100644
--- a/heatclient/common/http.py
+++ b/heatclient/common/http.py
@@ -160,7 +160,7 @@ class HTTPClient(object):
         self.log_http_response(resp, body_str)
 
         if 400 <= resp.status < 600:
-            raise exc.from_response(resp, body_iter)
+            raise exc.from_response(resp, body_str)
         elif resp.status in (301, 302, 305):
             # Redirected. Reissue the request to the new location.
             location = resp.getheader('location', None)
@@ -175,7 +175,7 @@ class HTTPClient(object):
                 raise exc.InvalidEndpoint(message=message)
             return self._http_request(location, method, **kwargs)
         elif resp.status == 300:
-            raise exc.from_response(resp, body_iter)
+            raise exc.from_response(resp, body_str)
 
         return resp, body_str
 
@@ -187,10 +187,10 @@ class HTTPClient(object):
         if 'body' in kwargs:
             kwargs['body'] = json.dumps(kwargs['body'])
 
-        resp, body_iter = self._http_request(url, method, **kwargs)
+        resp, body_str = self._http_request(url, method, **kwargs)
 
         if 'application/json' in resp.getheader('content-type', None):
-            body = ''.join([chunk for chunk in body_iter])
+            body = body_str
             try:
                 body = json.loads(body)
             except ValueError:
diff --git a/tests/test_common_http.py b/tests/test_common_http.py
index e32ce0ef..eb105906 100644
--- a/tests/test_common_http.py
+++ b/tests/test_common_http.py
@@ -183,7 +183,14 @@ class HttpClientTest(unittest.TestCase):
         # Replay, create client, assert
         self.m.ReplayAll()
         client = http.HTTPClient('http://example.com:8004')
-        self.assertRaises(exc.HTTPNotFound, client.json_request, 'GET', '')
+        try:
+            client.json_request('GET', '')
+            self.fail('No exception raised')
+        except exc.HTTPNotFound as e:
+            # Assert that the raised exception can be converted to string
+            self.assertNotEqual(e.message, None)
+        except:
+            raise
         self.m.VerifyAll()
 
     def test_http_300_json_request(self):
@@ -200,7 +207,14 @@ class HttpClientTest(unittest.TestCase):
         # Replay, create client, assert
         self.m.ReplayAll()
         client = http.HTTPClient('http://example.com:8004')
-        self.assertRaises(exc.HTTPMultipleChoices, client.json_request, 'GET', '')
+        try:
+            client.json_request('GET', '')
+            self.fail('No exception raised')
+        except exc.HTTPMultipleChoices as e:
+            # Assert that the raised exception can be converted to string
+            self.assertNotEqual(e.message, None)
+        except:
+            raise
         self.m.VerifyAll()
 
     #def test_https_json_request(self):