diff --git a/AWSIoTPythonSDK/core/greengrass/discovery/providers.py b/AWSIoTPythonSDK/core/greengrass/discovery/providers.py
index 47235c9..b09dfed 100644
--- a/AWSIoTPythonSDK/core/greengrass/discovery/providers.py
+++ b/AWSIoTPythonSDK/core/greengrass/discovery/providers.py
@@ -366,9 +366,14 @@ def _receive_until(self, ssl_sock, criteria_function, extra_data=None):
         start_time = time.time()
         response = bytearray()
         number_bytes_read = 0
+        ssl_sock_tmp = None
         while True:  # Python does not have do-while
             try:
-                response.extend(self._convert_to_int_py3(ssl_sock.read(1)))
+                ssl_sock_tmp = self._convert_to_int_py3(ssl_sock.read(1))
+                if ssl_sock_tmp is list:
+                    response.extend(ssl_sock_tmp)
+                else:
+                    response.append(ssl_sock_tmp)
                 number_bytes_read += 1
             except socket.error as err:
                 if err.errno == ssl.SSL_ERROR_WANT_READ or err.errno == ssl.SSL_ERROR_WANT_WRITE: