diff --git a/scripts/evaluations/clustering.py b/scripts/evaluations/clustering.py
index 148bf7f..765d950 100644
--- a/scripts/evaluations/clustering.py
+++ b/scripts/evaluations/clustering.py
@@ -31,7 +31,8 @@ if __name__ == "__main__":
                             "utt2"
                         ],
                         help="from features or from utt2?")
-    parser.add_argument("--prefix", 
+    parser.add_argument("--prefix",
+                        default="",
                         type=str,
                         help="prefix of saved files")
     parser.add_argument("--outdir",