diff --git a/src/TensorFlowNET.Core/Gradients/gradients_impl.py.cs b/src/TensorFlowNET.Core/Gradients/gradients_impl.py.cs
index 046732c1..d449eaf8 100644
--- a/src/TensorFlowNET.Core/Gradients/gradients_impl.py.cs
+++ b/src/TensorFlowNET.Core/Gradients/gradients_impl.py.cs
@@ -143,9 +143,6 @@ namespace Tensorflow
 
                                 }
                             });
-
-                            // temp fix name scope
-                            op.Graph._name_stack = "gradients";
                         }
                     }
                     else
diff --git a/src/TensorFlowNET.Core/Gradients/math_grad.py.cs b/src/TensorFlowNET.Core/Gradients/math_grad.py.cs
index f2b146a4..2560a2e5 100644
--- a/src/TensorFlowNET.Core/Gradients/math_grad.py.cs
+++ b/src/TensorFlowNET.Core/Gradients/math_grad.py.cs
@@ -48,7 +48,8 @@ namespace Tensorflow
             var reduce_sum1 = math_ops.reduce_sum(realdiv1, rx);
             var realdiv2 = gen_math_ops.real_div(-x, y);
             var realdiv3 = gen_math_ops.real_div(realdiv2, y);
-            var reduce_sum2 = math_ops.reduce_sum(grad * realdiv3, ry);
+            var mul = grad * realdiv3;
+            var reduce_sum2 = math_ops.reduce_sum(mul, ry);
 
             return (gen_array_ops.reshape(reduce_sum1, sx), gen_array_ops.reshape(reduce_sum2, sy));
         }
diff --git a/src/TensorFlowNET.Core/Graphs/Graph.cs b/src/TensorFlowNET.Core/Graphs/Graph.cs
index 3d46196d..dc25f853 100644
--- a/src/TensorFlowNET.Core/Graphs/Graph.cs
+++ b/src/TensorFlowNET.Core/Graphs/Graph.cs
@@ -23,7 +23,6 @@ namespace Tensorflow
         private List<String> _unfetchable_ops = new List<string>();
 
         public string _name_stack = "";
-        public string old_stack = "";
         public string _graph_key;
         public Status Status { get; }
 
@@ -180,8 +179,6 @@ namespace Tensorflow
 
         public string name_scope(string name)
         {
-            old_stack = _name_stack;
-
             string new_stack = "";
 
             if (name.EndsWith("/"))
diff --git a/src/TensorFlowNET.Core/Operations/array_ops.py.cs b/src/TensorFlowNET.Core/Operations/array_ops.py.cs
index df139aa3..56c6f715 100644
--- a/src/TensorFlowNET.Core/Operations/array_ops.py.cs
+++ b/src/TensorFlowNET.Core/Operations/array_ops.py.cs
@@ -94,10 +94,6 @@ namespace Tensorflow
                         return constant_op.constant(nd, name);
                     }
                 }
-                else
-                {
-                    // result = gen_array_ops.shape();
-                }
 
                 return gen_array_ops.shape(input);
             });
diff --git a/src/TensorFlowNET.Core/ops.name_scope.cs b/src/TensorFlowNET.Core/ops.name_scope.cs
index c0e60b52..0fee8330 100644
--- a/src/TensorFlowNET.Core/ops.name_scope.cs
+++ b/src/TensorFlowNET.Core/ops.name_scope.cs
@@ -14,6 +14,7 @@ namespace Tensorflow
             public object _values;
             public Context _ctx;
             public string _name_scope;
+            public string old_stack = "";
             private object _g_manager;
 
             public name_scope(string name, string default_name = "", object values = null)
@@ -38,15 +39,14 @@ namespace Tensorflow
                 if (g == null)
                     g = get_default_graph();
 
+                old_stack = g._name_stack;
                 _name_scope = g.name_scope(_name);
             }
 
             public void Dispose()
             {
                 var g = get_default_graph();
-                g._name_stack = g.old_stack;
-                // clear g._name_stack
-                g.old_stack = "";
+                g._name_stack = old_stack;
             }
 
             public void __exit__()
diff --git a/src/TensorFlowNET.Core/ops.py.cs b/src/TensorFlowNET.Core/ops.py.cs
index 823fc6fd..ff3b1c5b 100644
--- a/src/TensorFlowNET.Core/ops.py.cs
+++ b/src/TensorFlowNET.Core/ops.py.cs
@@ -294,11 +294,11 @@ namespace Tensorflow
                 switch (oper.type)
                 {
                     case "Add":
-                        return math_grad._AddGrad(op, out_grads);
+                        return math_grad._AddGrad(oper, out_grads);
                     case "Sum":
-                        return math_grad._SumGrad(op, out_grads);
+                        return math_grad._SumGrad(oper, out_grads);
                     case "RealDiv":
-                        return math_grad._RealDivGrad(op, out_grads);
+                        return math_grad._RealDivGrad(oper, out_grads);
                     default:
                         throw new NotImplementedException($"get_gradient_function {oper.type}");
                 }
diff --git a/test/TensorFlowNET.UnitTest/NameScopeTest.cs b/test/TensorFlowNET.UnitTest/NameScopeTest.cs
new file mode 100644
index 00000000..64b2bd1f
--- /dev/null
+++ b/test/TensorFlowNET.UnitTest/NameScopeTest.cs
@@ -0,0 +1,45 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Tensorflow;
+
+namespace TensorFlowNET.UnitTest
+{
+    [TestClass]
+    public class NameScopeTest : Python
+    {
+        Graph g = ops.get_default_graph();
+        string name = "";
+
+        [TestMethod]
+        public void NestedNameScope()
+        {
+            with<ops.name_scope>(new ops.name_scope("scope1"), scope1 =>
+            {
+                name = scope1;
+                Assert.AreEqual("scope1", g._name_stack);
+                Assert.AreEqual("scope1/", name);
+
+                var const1 = tf.constant(1.0);
+                Assert.AreEqual("scope1/Const:0", const1.name);
+
+                with<ops.name_scope>(new ops.name_scope("scope2"), scope2 =>
+                {
+                    name = scope2;
+                    Assert.AreEqual("scope1/scope2", g._name_stack);
+                    Assert.AreEqual("scope1/scope2/", name);
+
+                    var const2 = tf.constant(2.0);
+                    Assert.AreEqual("scope1/scope2/Const:0", const2.name);
+                });
+
+                Assert.AreEqual("scope1", g._name_stack);
+                var const3 = tf.constant(2.0);
+                Assert.AreEqual("scope1/Const_1:0", const3.name);
+            });
+
+            Assert.AreEqual("", g._name_stack);
+        }
+    }
+}