diff --git a/Exts.cs b/Exts.cs
index e2d9e53..cc7ee61 100644
--- a/Exts.cs
+++ b/Exts.cs
@@ -1,6 +1,20 @@
+using System.Diagnostics;
+
 static class Exts
 {
     public static string Unix(this string it) { return it.ReplaceLineEndings("\n"); }
     public static string NoEOL(this string it) { return it.ReplaceLineEndings(" "); }
     public static void Z(this int it) { if (it != 0) throw new Exception("result not zero"); }
+
+    public static string? GetFileNameOrDefault(this Process p)
+    {
+        try
+        {
+            return p.MainModule?.FileName;
+        }
+        catch
+        {
+            return null;
+        }
+    }
 }
\ No newline at end of file
diff --git a/Program.cs b/Program.cs
index 97f33e6..13f93e5 100644
--- a/Program.cs
+++ b/Program.cs
@@ -1,4 +1,5 @@
 using System.Collections.Immutable;
+using System.Diagnostics;
 using System.IO.Compression;
 using System.Security.Cryptography;
 using System.Security.Principal;
@@ -144,6 +145,12 @@ static void Main(string[] args)
             return;
         }
 
+        if (Process.GetProcesses().Any(p => p.GetFileNameOrDefault() == serviceExe))
+        {
+            Console.WriteLine($"Please quit Google Play Games.");
+            return;
+        }
+
         if (!File.Exists(stockBios))
         {
             Console.WriteLine("\n\n############# Backup bios.rom");
@@ -186,30 +193,39 @@ static void Main(string[] args)
     static void PatchServiceExe(string exePath, string outPath)
     {
         Environment.CurrentDirectory = Path.GetDirectoryName(exePath)!;
-        var assembly = AssemblyDefinition.ReadAssembly(exePath, new ReaderParameters { AssemblyResolver = new DefaultAssemblyResolver() });
-        var module = assembly.MainModule;
+        try
+        {
 
-        // System.Void Google.Hpe.Service.AppSession.AppSessionScope::HandleEmulatorSurfaceStateUpdate(Google.Hpe.Service.Emulator.Surface.EmulatorSurfaceState,Google.Hpe.Service.Emulator.Surface.EmulatorSurfaceState)
-        var AppSessionScope = module.GetType("Google.Hpe.Service.AppSession.AppSessionScope");
-        var method = AppSessionScope.Methods.Single(x => x.Name == "HandleEmulatorSurfaceStateUpdate");
+            var assembly = AssemblyDefinition.ReadAssembly(exePath, new ReaderParameters { AssemblyResolver = new DefaultAssemblyResolver() });
+            var module = assembly.MainModule;
 
-        Instruction? instruct = method.Body.Instructions.FirstOrDefault(p => p.Operand is FieldDefinition f && f.Name == "_transientForegroundPackages");
+            // System.Void Google.Hpe.Service.AppSession.AppSessionScope::HandleEmulatorSurfaceStateUpdate(Google.Hpe.Service.Emulator.Surface.EmulatorSurfaceState,Google.Hpe.Service.Emulator.Surface.EmulatorSurfaceState)
+            var AppSessionScope = module.GetType("Google.Hpe.Service.AppSession.AppSessionScope");
+            var method = AppSessionScope.Methods.Single(x => x.Name == "HandleEmulatorSurfaceStateUpdate");
+            var instructions = method.Body.Instructions;
 
-        if (instruct == null)
-        {
-            Console.WriteLine("nothing to patch.");
-            return;
-        }
+            var begin = instructions.FirstOrDefault(p => p.Operand is FieldDefinition f && f.Name == "_transientForegroundPackages");
 
-        Console.WriteLine($"Patch Instruction at {method.Body.Instructions.IndexOf(instruct)}");
+            if (begin == null)
+            {
+                Console.WriteLine("nothing to patch.");
+                return;
+            }
 
-        var processor = method.Body.GetILProcessor();
-        var newInstruction = processor.Create(OpCodes.Ret);
+            var idx = instructions.IndexOf(begin);
+            Console.WriteLine($"Patch Instruction at idx {idx}, offset IL_{begin.Offset:X4}");
 
-        processor.Replace(instruct, newInstruction);
+            while (instructions[idx].OpCode != OpCodes.Leave_S)
+            {
+                instructions.RemoveAt(idx);
+            }
 
-        assembly.Write(outPath);
-        Environment.CurrentDirectory = StartDirectory;
+            assembly.Write(outPath);
+        }
+        finally
+        {
+            Environment.CurrentDirectory = StartDirectory;
+        }
     }
 
     static byte[] ExtractBoot(string diskPath)