diff --git a/src/erlazure_blob.erl b/src/erlazure_blob.erl
index 61008d7..681b41b 100644
--- a/src/erlazure_blob.erl
+++ b/src/erlazure_blob.erl
@@ -38,7 +38,7 @@
 -export([parse_container_list/1, parse_blob_list/1, get_request_body/1, parse_block_list/1,
          get_request_param_specs/0, parse_blob_response/1]).
 
--spec parse_container_list(string()) -> {error, bad_response} | {[blob_container()], list()}.
+-spec parse_container_list(string() | binary()) -> {error, bad_response} | {ok, {[blob_container()], list()}}.
 parse_container_list(Response) ->
         ParserSpec = #enum_parser_spec { rootKey = 'Containers',
                                          elementKey = 'Container',