diff --git a/audiomate/corpus/io/default.py b/audiomate/corpus/io/default.py
index <HASH>..<HASH> 100644
--- a/audiomate/corpus/io/default.py
+++ b/audiomate/corpus/io/default.py
@@ -307,7 +307,8 @@ class DefaultWriter(base.CorpusWriter):
 
             data[issuer.idx] = issuer_data
 
-        jsonfile.write_json_to_file(file_path, data)
+        with open(file_path, 'w', encoding='utf-8') as f:
+            json.dump(data, f)
 
     @staticmethod
     def write_utterances(utterance_path, corpus):
diff --git a/audiomate/corpus/io/voxforge.py b/audiomate/corpus/io/voxforge.py
index <HASH>..<HASH> 100644
--- a/audiomate/corpus/io/voxforge.py
+++ b/audiomate/corpus/io/voxforge.py
@@ -134,7 +134,7 @@ class VoxforgeReader(base.CorpusReader):
     def _load(self, path):
         corpus = audiomate.Corpus(path=path)
 
-        for dir_path in VoxforgeReader.data_folders(path):
+        for dir_path in sorted(VoxforgeReader.data_folders(path)):
             item = os.path.basename(dir_path)
             etc_folder = os.path.join(dir_path, 'etc')
             wav_folder = os.path.join(dir_path, 'wav')
Fix voxforge reading to be deterministic