diff --git a/test/Compiler.Tests/Emit/ImportedExtensionDeclaringAssemblyInvariantEmitTests.cs b/test/Compiler.Tests/Emit/ImportedExtensionDeclaringAssemblyInvariantEmitTests.cs
new file mode 100644
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+++ b/test/Compiler.Tests/Emit/ImportedExtensionDeclaringAssemblyInvariantEmitTests.cs
@@ -0,0 +1,209 @@
+// <copyright file="ImportedExtensionDeclaringAssemblyInvariantEmitTests.cs" company="GSharp">
+// Copyright (C) GSharp Authors. All rights reserved.
+// </copyright>
+
+using System;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+using System.Reflection.Metadata;
+using System.Reflection.PortableExecutable;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Xunit;
+
+namespace GSharp.Compiler.Tests.Emit;
+
+/// <summary>
+/// Verifies that an imported extension method's MemberRef retains its
+/// <see cref="System.Reflection.MethodInfo.DeclaringType"/> assembly identity
+/// when another reference defines the same fully-qualified host type.
+/// </summary>
+public sealed class ImportedExtensionDeclaringAssemblyInvariantEmitTests
+{
+    private const string PrimarySource = """
+        namespace ClassLibrary1;
+
+        public sealed class A { }
+
+        public static class B
+        {
+            public static string Call(this A value) => "correct";
+        }
+        """;
+
+    private const string ShadowSource = """
+        namespace ClassLibrary1;
+
+        public static class B
+        {
+            public static string Shadow(this A value) => "shadow";
+        }
+        """;
+
+    private const string GSharpSource = """
+        package MyApp
+
+        import System
+        import ClassLibrary1
+
+        var a = A()
+        Console.WriteLine(a.Call())
+        """;
+
+    [Theory]
+    [InlineData(false)]
+    [InlineData(true)]
+    public void MemberRef_PreservesDeclaringAssembly_RegardlessOfReferenceOrder(bool shadowReferenceFirst)
+    {
+        using var artifacts = Compile(shadowReferenceFirst);
+
+        IlVerifier.Verify(
+            artifacts.OutputPath,
+            additionalReferences: new[] { artifacts.PrimaryPath, artifacts.ShadowPath });
+
+        using var stream = File.OpenRead(artifacts.OutputPath);
+        using var peReader = new PEReader(stream);
+        var reader = peReader.GetMetadataReader();
+        var callHandle = Assert.Single(
+            reader.MemberReferences,
+            handle => reader.GetString(reader.GetMemberReference(handle).Name) == "Call");
+        var call = reader.GetMemberReference(callHandle);
+        Assert.Equal(HandleKind.TypeReference, call.Parent.Kind);
+        var parent = reader.GetTypeReference((TypeReferenceHandle)call.Parent);
+        Assert.Equal(HandleKind.AssemblyReference, parent.ResolutionScope.Kind);
+        var assembly = reader.GetAssemblyReference((AssemblyReferenceHandle)parent.ResolutionScope);
+
+        Assert.Equal("ClassLibrary1", reader.GetString(assembly.Name));
+        Assert.Equal("correct\n", Run(artifacts.OutputPath));
+    }
+
+    private static CompilationArtifacts Compile(bool shadowReferenceFirst)
+    {
+        var directory = Path.Combine(
+            AppContext.BaseDirectory,
+            "imported-extension-assembly-identity-artifacts",
+            Guid.NewGuid().ToString("N"));
+        Directory.CreateDirectory(directory);
+
+        var primaryPath = Path.Combine(directory, "ClassLibrary1.dll");
+        EmitFixture("ClassLibrary1", PrimarySource, primaryPath);
+        var shadowPath = Path.Combine(directory, "AClassLibrary3.dll");
+        EmitFixture(
+            "AClassLibrary3",
+            ShadowSource,
+            shadowPath,
+            new[] { MetadataReference.CreateFromFile(primaryPath) });
+
+        var sourcePath = Path.Combine(directory, "Program.gs");
+        var outputPath = Path.Combine(directory, "MyApp.dll");
+        File.WriteAllText(sourcePath, GSharpSource);
+
+        using var stdout = new StringWriter();
+        using var stderr = new StringWriter();
+        var previousOut = Console.Out;
+        var previousError = Console.Error;
+        Console.SetOut(stdout);
+        Console.SetError(stderr);
+        int exitCode;
+        try
+        {
+            var firstReference = shadowReferenceFirst ? shadowPath : primaryPath;
+            var secondReference = shadowReferenceFirst ? primaryPath : shadowPath;
+            exitCode = Program.Main(
+                new[]
+                {
+                    "/out:" + outputPath,
+                    "/target:exe",
+                    "/targetframework:net10.0",
+                    "/reference:" + firstReference,
+                    "/reference:" + secondReference,
+                    sourcePath,
+                });
+        }
+        finally
+        {
+            Console.SetOut(previousOut);
+            Console.SetError(previousError);
+        }
+
+        var diagnostics = stdout.ToString() + stderr.ToString();
+        Assert.True(exitCode == 0, $"gsc failed:\n{diagnostics}");
+        return new CompilationArtifacts(directory, primaryPath, shadowPath, outputPath);
+    }
+
+    private static void EmitFixture(
+        string assemblyName,
+        string source,
+        string path,
+        MetadataReference[] additionalReferences = null)
+    {
+        var references = ((string)AppContext.GetData("TRUSTED_PLATFORM_ASSEMBLIES")!)
+            .Split(Path.PathSeparator)
+            .Select(reference => MetadataReference.CreateFromFile(reference))
+            .Concat(additionalReferences ?? Array.Empty<MetadataReference>());
+        var compilation = CSharpCompilation.Create(
+            assemblyName,
+            new[] { CSharpSyntaxTree.ParseText(source) },
+            references,
+            new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary));
+        var result = compilation.Emit(path);
+        Assert.True(result.Success, string.Join(Environment.NewLine, result.Diagnostics));
+    }
+
+    private static string Run(string assemblyPath)
+    {
+        var startInfo = new ProcessStartInfo("dotnet")
+        {
+            RedirectStandardOutput = true,
+            RedirectStandardError = true,
+            UseShellExecute = false,
+            WorkingDirectory = Path.GetDirectoryName(assemblyPath)!,
+        };
+        startInfo.ArgumentList.Add("exec");
+        startInfo.ArgumentList.Add("--runtimeconfig");
+        startInfo.ArgumentList.Add(Path.ChangeExtension(assemblyPath, ".runtimeconfig.json"));
+        startInfo.ArgumentList.Add(assemblyPath);
+
+        using var process = Process.Start(startInfo)!;
+        var stdout = process.StandardOutput.ReadToEnd();
+        var stderr = process.StandardError.ReadToEnd();
+        Assert.True(process.WaitForExit(30_000), "dotnet exec timed out.");
+        Assert.True(process.ExitCode == 0, $"exited {process.ExitCode}\n{stderr}");
+        return stdout.Replace("\r\n", "\n", StringComparison.Ordinal);
+    }
+
+    private sealed class CompilationArtifacts : IDisposable
+    {
+        public CompilationArtifacts(
+            string directory,
+            string primaryPath,
+            string shadowPath,
+            string outputPath)
+        {
+            Directory = directory;
+            PrimaryPath = primaryPath;
+            ShadowPath = shadowPath;
+            OutputPath = outputPath;
+        }
+
+        public string Directory { get; }
+
+        public string PrimaryPath { get; }
+
+        public string ShadowPath { get; }
+
+        public string OutputPath { get; }
+
+        public void Dispose()
+        {
+            try
+            {
+                System.IO.Directory.Delete(Directory, recursive: true);
+            }
+            catch
+            {
+            }
+        }
+    }
+}