diff --git a/WelsonJS.Toolkit/WelsonJS.Launcher/ZipExtractor.cs b/WelsonJS.Toolkit/WelsonJS.Launcher/ZipExtractor.cs
index a194fda..bcf60d7 100644
--- a/WelsonJS.Toolkit/WelsonJS.Launcher/ZipExtractor.cs
+++ b/WelsonJS.Toolkit/WelsonJS.Launcher/ZipExtractor.cs
@@ -170,8 +170,11 @@ namespace WelsonJS.Launcher
                 return false;
 
             dynamic shell = Activator.CreateInstance(shellAppType);
+            if (shell == null)
+                return false;
             dynamic zip = shell.NameSpace(filePath);
             dynamic dest = shell.NameSpace(workingDirectory);
+            dynamic dest = shell.NameSpace(workingDirectory);
 
             if (zip == null || dest == null)
                 return false;