diff --git a/nnvm/python/nnvm/frontend/onnx.py b/nnvm/python/nnvm/frontend/onnx.py
index 5457f763f23c0cf6c756238bb6c7cb177ec5fec5..b34d3bbd8283c4eb357ca2ec7558510d4f6b3f43 100644
--- a/nnvm/python/nnvm/frontend/onnx.py
+++ b/nnvm/python/nnvm/frontend/onnx.py
@@ -217,7 +217,7 @@ def _softsign():
 
 def _softplus():
     def _impl(inputs, attr, params):
-        return _sym.log(_sym.exp(x) + 1)
+        return _sym.log(_sym.exp(inputs[0]) + 1)
     return _impl
 
 def _pad():