diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/ResourceIncludeTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/ResourceIncludeTests.cs
index a6b930962e..9a008503f5 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/ResourceIncludeTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/ResourceIncludeTests.cs
@@ -2,6 +2,8 @@
 using System.Collections.Generic;
 using Avalonia.Controls;
 using Avalonia.Media;
+using Avalonia.Metadata;
+using Avalonia.Styling;
 using Avalonia.UnitTests;
 using Xunit;
 
@@ -9,87 +11,146 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
 {
     public class ResourceIncludeTests : XamlTestBase
     {
-        public class StaticResourceExtensionTests : XamlTestBase
+        [Fact]
+        public void ResourceInclude_Loads_ResourceDictionary()
         {
-            [Fact]
-            public void ResourceInclude_Loads_ResourceDictionary()
+            var documents = new[]
             {
-                var documents = new[]
-                {
-                    new RuntimeXamlLoaderDocument(new Uri("avares://Tests/Resource.xaml"), @"
+                new RuntimeXamlLoaderDocument(new Uri("avares://Tests/Resource.xaml"), @"
 <ResourceDictionary xmlns='https://github.com/avaloniaui'
-                    xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
-    <SolidColorBrush x:Key='brush'>#ff506070</SolidColorBrush>
+                xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+<SolidColorBrush x:Key='brush'>#ff506070</SolidColorBrush>
 </ResourceDictionary>"),
-                    new RuntimeXamlLoaderDocument(@"
+                new RuntimeXamlLoaderDocument(@"
 <UserControl xmlns='https://github.com/avaloniaui'
-             xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
-    <UserControl.Resources>
-        <ResourceDictionary>
-            <ResourceDictionary.MergedDictionaries>
-                <ResourceInclude Source='avares://Tests/Resource.xaml'/>
-            </ResourceDictionary.MergedDictionaries>
-        </ResourceDictionary>
-    </UserControl.Resources>
-
-    <Border Name='border' Background='{StaticResource brush}'/>
+         xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+<UserControl.Resources>
+    <ResourceDictionary>
+        <ResourceDictionary.MergedDictionaries>
+            <ResourceInclude Source='avares://Tests/Resource.xaml'/>
+        </ResourceDictionary.MergedDictionaries>
+    </ResourceDictionary>
+</UserControl.Resources>
+
+<Border Name='border' Background='{StaticResource brush}'/>
 </UserControl>")
-                };
+            };
 
-                using (StartWithResources())
-                {
-                    var compiled = AvaloniaRuntimeXamlLoader.LoadGroup(documents);
-                    var userControl = Assert.IsType<UserControl>(compiled[1]);
-                    var border = userControl.FindControl<Border>("border");
+            using (StartWithResources())
+            {
+                var compiled = AvaloniaRuntimeXamlLoader.LoadGroup(documents);
+                var userControl = Assert.IsType<UserControl>(compiled[1]);
+                var border = userControl.FindControl<Border>("border");
 
-                    var brush = (ISolidColorBrush)border.Background;
-                    Assert.Equal(0xff506070, brush.Color.ToUInt32());
-                }
+                var brush = (ISolidColorBrush)border.Background;
+                Assert.Equal(0xff506070, brush.Color.ToUInt32());
             }
+        }
 
-            [Fact]
-            public void Missing_ResourceKey_In_ResourceInclude_Does_Not_Cause_StackOverflow()
+        [Fact]
+        public void Missing_ResourceKey_In_ResourceInclude_Does_Not_Cause_StackOverflow()
+        {
+            var app = Application.Current;
+            var documents = new[]
             {
-                var app = Application.Current;
-                var documents = new[]
-                {
-                    new RuntimeXamlLoaderDocument(new Uri("avares://Tests/Resource.xaml"), @"
+                new RuntimeXamlLoaderDocument(new Uri("avares://Tests/Resource.xaml"), @"
 <ResourceDictionary xmlns='https://github.com/avaloniaui'
-                    xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
-    <StaticResource x:Key='brush' ResourceKey='missing' />
+                xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+<StaticResource x:Key='brush' ResourceKey='missing' />
 </ResourceDictionary>"),
-                    new RuntimeXamlLoaderDocument(app, @"
+                new RuntimeXamlLoaderDocument(app, @"
 <Application xmlns='https://github.com/avaloniaui'
-             xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
-    <Application.Resources>
-        <ResourceDictionary>
-            <ResourceDictionary.MergedDictionaries>
-                <ResourceInclude Source='avares://Tests/Resource.xaml'/>
-            </ResourceDictionary.MergedDictionaries>
-        </ResourceDictionary>
-    </Application.Resources>
+         xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+<Application.Resources>
+    <ResourceDictionary>
+        <ResourceDictionary.MergedDictionaries>
+            <ResourceInclude Source='avares://Tests/Resource.xaml'/>
+        </ResourceDictionary.MergedDictionaries>
+    </ResourceDictionary>
+</Application.Resources>
 </Application>")
-                };
+            };
 
-                using (StartWithResources())
+            using (StartWithResources())
+            {
+                try
                 {
-                    try
-                    {
-                        AvaloniaRuntimeXamlLoader.LoadGroup(documents);
-                    }
-                    catch (KeyNotFoundException)
-                    {
-
-                    }
+                    AvaloniaRuntimeXamlLoader.LoadGroup(documents);
                 }
+                catch (KeyNotFoundException)
+                {
+
+                }
+            }
+        }
+        
+        [Fact]
+        public void ResourceInclude_Should_Be_Allowed_To_Have_Key_In_Custom_Container()
+        {
+            var app = Application.Current;
+            var documents = new[]
+            {
+                new RuntimeXamlLoaderDocument(new Uri("avares://Demo/en-us.axaml"), @"
+<ResourceDictionary xmlns='https://github.com/avaloniaui'
+                    xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
+    <x:String x:Key='OkButton'>OK</x:String>
+</ResourceDictionary>"),
+                new RuntimeXamlLoaderDocument(app, @"
+<ResourceDictionary xmlns='https://github.com/avaloniaui'
+                    xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+                    xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.MarkupExtensions;assembly=Avalonia.Markup.Xaml.UnitTests'>
+    <ResourceDictionary.MergedDictionaries>
+        <local:LocaleCollection>
+            <ResourceInclude Source='avares://Demo/en-us.axaml' x:Key='English' />
+        </local:LocaleCollection>
+    </ResourceDictionary.MergedDictionaries>
+</ResourceDictionary>")
+            };
+
+            using (StartWithResources())
+            {
+                var groups = AvaloniaRuntimeXamlLoader.LoadGroup(documents);
+                var res = Assert.IsType<ResourceDictionary>(groups[1]);
+
+                Assert.True(res.TryGetResource("OkButton", null, out var val));
+                Assert.Equal("OK", val);
             }
+        }
 
-            private IDisposable StartWithResources(params (string, string)[] assets)
+        private IDisposable StartWithResources(params (string, string)[] assets)
+        {
+            var assetLoader = new MockAssetLoader(assets);
+            var services = new TestServices(assetLoader: assetLoader);
+            return UnitTestApplication.Start(services);
+        }
+    }
+    
+    // See https://github.com/AvaloniaUI/Avalonia/issues/11172
+    public class LocaleCollection : IResourceProvider
+    {
+        private readonly Dictionary<object, IResourceProvider> _langs = new();
+
+        public IResourceHost Owner { get; private set; }
+
+        public bool HasResources => true;
+
+        public event EventHandler OwnerChanged;
+
+        public void AddOwner(IResourceHost owner) => Owner = owner;
+
+        public void RemoveOwner(IResourceHost owner) => Owner = null;
+
+        public bool TryGetResource(object key, ThemeVariant theme, out object? value)
+        {
+            if (_langs.TryGetValue("English", out var res))
             {
-                var assetLoader = new MockAssetLoader(assets);
-                var services = new TestServices(assetLoader: assetLoader);
-                return UnitTestApplication.Start(services);
+                return res.TryGetResource(key, theme, out value);
             }
+            value = null;
+            return false;
         }
+
+        // Allow Avalonia to use this class as a collection, requires x:Key on the IResourceProvider 
+        public void Add(object k, IResourceProvider v) => _langs.Add(k, v);
     }
 }