diff --git a/example/warpctc/toy_ctc.py b/example/warpctc/toy_ctc.py
index 08a48d2b7f4c..46bab5776018 100644
--- a/example/warpctc/toy_ctc.py
+++ b/example/warpctc/toy_ctc.py
@@ -36,10 +36,10 @@ def gen_rand():
     buf = str(num)
     while len(buf) < 4:
         buf = "0" + buf
-    ret = np.array([])
+    ret = []
     for i in range(80):
         c = int(buf[i // 20])
-        ret = np.concatenate([ret, gen_feature(c)])
+        ret.append(gen_feature(c))
     return buf, ret
 
 def get_label(buf):
@@ -56,7 +56,7 @@ def __init__(self, count, batch_size, num_label, init_states):
         self.num_label = num_label
         self.init_states = init_states
         self.init_state_arrays = [mx.nd.zeros(x[1]) for x in init_states]
-        self.provide_data = [('data', (batch_size, 10 * 80))] + init_states
+        self.provide_data = [('data', (batch_size, 80, 10))] + init_states
         self.provide_label = [('label', (self.batch_size, 4))]
 
     def __iter__(self):