diff --git a/python/mxnet/recordio.py b/python/mxnet/recordio.py
index eb861147b967..b1d972e9cfe4 100644
--- a/python/mxnet/recordio.py
+++ b/python/mxnet/recordio.py
@@ -245,10 +245,11 @@ def __init__(self, idx_path, uri, flag, key_type=int):
 
     def open(self):
         super(MXIndexedRecordIO, self).open()
-        self.idx = {}
-        self.keys = []
         self.fidx = open(self.idx_path, self.flag)
-        if not self.writable:
+        if self.writable:
+            self.idx = {}
+            self.keys = []
+        elif not self.idx:
             for line in iter(self.fidx.readline, ''):
                 line = line.strip().split('\t')
                 key = self.key_type(line[0])