diff --git a/dotnet/targets/Xamarin.Shared.Sdk.targets b/dotnet/targets/Xamarin.Shared.Sdk.targets
index 2fbe4850aabe..4e8cf77cc143 100644
--- a/dotnet/targets/Xamarin.Shared.Sdk.targets
+++ b/dotnet/targets/Xamarin.Shared.Sdk.targets
@@ -1164,6 +1164,15 @@
 		</ItemGroup>
 	</Target>
 
+	<!-- https://github.com/xamarin/xamarin-macios/issues/19037 -->
+	<!-- The trimmer will set the RootMode for the current assembly to 'EntryPoint', but that doesn't work for app extension projects, because those are library projects that don't have entry points.
+		 So here we set RootMode=Library for these cases. -->
+	<Target Name="_FixRootAssemblyForAppExtensions" AfterTargets="PrepareForILLink" Condition="'$(IsAppExtension)' == 'true'">
+		<ItemGroup>
+			<TrimmerRootAssembly Update="@(TrimmerRootAssembly)" Condition=" '%(TrimmerRootAssembly.RootMode)' == 'EntryPoint' " RootMode="Library" />
+		</ItemGroup>
+	</Target>
+
 	<Target Name="_CreateAOTDedupAssembly"
 			Condition="'$(_RunAotCompiler)' == 'true' And '$(IsMacEnabled)' == 'true'"
 			DependsOnTargets="_ComputeManagedAssemblyToLink"
diff --git a/tests/dotnet/UnitTests/ProjectTest.cs b/tests/dotnet/UnitTests/ProjectTest.cs
index e6496cc8ce77..007d5f4e41f8 100644
--- a/tests/dotnet/UnitTests/ProjectTest.cs
+++ b/tests/dotnet/UnitTests/ProjectTest.cs
@@ -1009,6 +1009,24 @@ public void BuildProjectsWithExtensionsAndFrameworks (ApplePlatform platform)
 			ExecuteWithMagicWordAndAssert (platform, runtimeIdentifiers, appExecutable);
 		}
 
+
+		[TestCase (ApplePlatform.iOS)]
+		[TestCase (ApplePlatform.TVOS)]
+		[TestCase (ApplePlatform.MacOSX)]
+		// [TestCase ("MacCatalyst", "")] - No extension support yet
+		public void BuildTrimmedExtensionProject (ApplePlatform platform)
+		{
+			Configuration.IgnoreIfIgnoredPlatform (platform);
+			var project_path = GetProjectPath ("ExtensionProject", platform: platform);
+
+			Clean (project_path);
+
+			var properties = GetDefaultProperties ();
+			properties ["MtouchLink"] = "Full";
+			properties ["LinkMode"] = "Full";
+			DotNet.AssertBuild (project_path, properties);
+		}
+
 		[TestCase (ApplePlatform.iOS, "iossimulator-x64;iossimulator-arm64")]
 		[TestCase (ApplePlatform.TVOS, "tvossimulator-x64")]
 		[TestCase (ApplePlatform.MacCatalyst, "maccatalyst-x64")]