diff --git a/src/TensorFlowNET.Core/Graphs/Graph.Import.cs b/src/TensorFlowNET.Core/Graphs/Graph.Import.cs
index af7ebfd1..1c91868b 100644
--- a/src/TensorFlowNET.Core/Graphs/Graph.Import.cs
+++ b/src/TensorFlowNET.Core/Graphs/Graph.Import.cs
@@ -59,12 +59,16 @@ namespace Tensorflow
             return status;
         }
 
+        static object locker = new object();
         public static Graph ImportFromPB(string file_path, string name = null)
         {
-            var graph = tf.Graph().as_default();
-            var graph_def = GraphDef.Parser.ParseFrom(File.ReadAllBytes(file_path));
-            importer.import_graph_def(graph_def, name: name);
-            return graph;
+            lock (locker)
+            {
+                var graph = tf.Graph().as_default();
+                var graph_def = GraphDef.Parser.ParseFrom(File.ReadAllBytes(file_path));
+                importer.import_graph_def(graph_def, name: name);
+                return graph;
+            }
         }
     }
 }
diff --git a/src/TensorFlowNET.Core/Graphs/Graph.Operation.cs b/src/TensorFlowNET.Core/Graphs/Graph.Operation.cs
index 09e09573..1030922b 100644
--- a/src/TensorFlowNET.Core/Graphs/Graph.Operation.cs
+++ b/src/TensorFlowNET.Core/Graphs/Graph.Operation.cs
@@ -55,7 +55,13 @@ namespace Tensorflow
 
         public Operation OperationByName(string operName)
         {
-            return c_api.TF_GraphOperationByName(_handle, operName);
+            var handle = c_api.TF_GraphOperationByName(_handle, operName);
+            if(graph_key != tf.get_default_graph().graph_key)
+            {
+                Console.WriteLine($"Current graph is not default graph.");
+                // throw new ValueError($"Current graph is not default graph.");
+            }
+            return new Operation(handle, g: this);
         }
 
         public ITensorOrOperation[] get_operations()
diff --git a/src/TensorFlowNET.Core/TensorFlowNET.Core.csproj b/src/TensorFlowNET.Core/TensorFlowNET.Core.csproj
index a6803448..17b5191b 100644
--- a/src/TensorFlowNET.Core/TensorFlowNET.Core.csproj
+++ b/src/TensorFlowNET.Core/TensorFlowNET.Core.csproj
@@ -5,7 +5,7 @@
     <AssemblyName>TensorFlow.NET</AssemblyName>
     <RootNamespace>Tensorflow</RootNamespace>
     <TargetTensorFlow>1.14.0</TargetTensorFlow>
-    <Version>0.10.8</Version>
+    <Version>0.10.9</Version>
     <Authors>Haiping Chen, Meinrad Recheis</Authors>
     <Company>SciSharp STACK</Company>
     <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
@@ -17,7 +17,7 @@
     <PackageTags>TensorFlow, NumSharp, SciSharp, MachineLearning, TensorFlow.NET, C#</PackageTags>
     <Description>Google's TensorFlow full binding in .NET Standard.
 Docs: https://tensorflownet.readthedocs.io</Description>
-    <AssemblyVersion>0.10.8.0</AssemblyVersion>
+    <AssemblyVersion>0.10.9.0</AssemblyVersion>
     <PackageReleaseNotes>Changes since v0.9.0:
 
 1. Added full connected Convolution Neural Network example.
@@ -37,7 +37,7 @@ Docs: https://tensorflownet.readthedocs.io</Description>
 15. Fix Tensor memory leak.
 16. Rename with to tf_with that is only used to build graph purpose.</PackageReleaseNotes>
     <LangVersion>7.3</LangVersion>
-    <FileVersion>0.10.8.0</FileVersion>
+    <FileVersion>0.10.9.0</FileVersion>
     <PackageLicenseFile>LICENSE</PackageLicenseFile>
     <PackageRequireLicenseAcceptance>true</PackageRequireLicenseAcceptance>
     <SignAssembly>true</SignAssembly>