diff --git a/src/Framework/Framework/CallerArgumentExpressionAttribute.cs b/src/Framework/Framework/CallerArgumentExpressionAttribute.cs
new file mode 100644
index 0000000000..2c156103a3
--- /dev/null
+++ b/src/Framework/Framework/CallerArgumentExpressionAttribute.cs
@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+ 
+namespace System.Runtime.CompilerServices
+{
+#if !NET5_0_OR_GREATER
+    [AttributeUsage(AttributeTargets.Parameter, AllowMultiple = false, Inherited = false)]
+    internal sealed class CallerArgumentExpressionAttribute : Attribute
+    {
+        public CallerArgumentExpressionAttribute(string parameterName)
+        {
+            ParameterName = parameterName;
+        }
+ 
+        public string ParameterName { get; }
+    }
+#endif
+}
diff --git a/src/Framework/Framework/Controls/KnockoutHelper.cs b/src/Framework/Framework/Controls/KnockoutHelper.cs
index 95e0340024..48416b83fd 100644
--- a/src/Framework/Framework/Controls/KnockoutHelper.cs
+++ b/src/Framework/Framework/Controls/KnockoutHelper.cs
@@ -428,7 +428,7 @@ private static JsExpression TransformOptionValueToExpression(DotvvmBindableObjec
             }
             else
             {
-                return $"[{handlerNameJson},{{q:{MakeStringLiteral(queueName)}}}]";
+                return $"[{handlerNameJson},{{q:{MakeStringLiteral(queueName!)}}}]";
             }
         }
         
diff --git a/src/Framework/Framework/Utils/ThrowHelpers.cs b/src/Framework/Framework/Utils/ThrowHelpers.cs
new file mode 100644
index 0000000000..875c1104d8
--- /dev/null
+++ b/src/Framework/Framework/Utils/ThrowHelpers.cs
@@ -0,0 +1,28 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.Runtime.CompilerServices;
+
+namespace DotVVM.Framework.Utils
+{
+    internal static class ThrowHelpers
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void ArgumentNull([NotNull] object? argument, [CallerArgumentExpression(nameof(argument))] string? paramName = null)
+        {
+#if NET6_OR_GREATER
+            ArgumentNullException.ThrowIfNull(value);
+#else
+            if (argument is null)
+            {
+                ThrowArgumentNullException(paramName);
+            }
+        }
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        [DoesNotReturn]
+        private static void ThrowArgumentNullException(string? paramName)
+        {
+            throw new ArgumentNullException(paramName);
+#endif
+        }
+    }
+}
diff --git a/src/Framework/Framework/ViewModel/Serialization/DefaultViewModelSerializer.cs b/src/Framework/Framework/ViewModel/Serialization/DefaultViewModelSerializer.cs
index 90088b1cb2..714b81eab2 100644
--- a/src/Framework/Framework/ViewModel/Serialization/DefaultViewModelSerializer.cs
+++ b/src/Framework/Framework/ViewModel/Serialization/DefaultViewModelSerializer.cs
@@ -22,6 +22,7 @@
 using Microsoft.Extensions.Logging;
 using DotVVM.Framework.Runtime.Tracing;
 using Microsoft.Extensions.DependencyInjection;
+using System.Text.Encodings.Web;
 
 namespace DotVVM.Framework.ViewModel.Serialization
 {
@@ -338,16 +339,26 @@ private List<NamedResource> SerializeResources(IDotvvmRequestContext context, Fu
         /// <summary>
         /// Serializes the redirect action.
         /// </summary>
-        public static string GenerateRedirectActionResponse(string url, bool replace, bool allowSpa, string? downloadName)
+        /// <return>UTF-8 encoded JSON response</return>
+        public static byte[] GenerateRedirectActionResponse(string url, bool replace, bool allowSpa, string? downloadName)
         {
+            ThrowHelpers.ArgumentNull(url);
             // create result object
-            return JsonSerializer.Serialize(new {
-                url,
-                action = "redirect",
-                replace,
-                allowSpa,
-                download = downloadName
-            }, DefaultSerializerSettingsProvider.Instance.SettingsHtmlUnsafe);
+            var result = new MemoryStream();
+            using (var w = new Utf8JsonWriter(result, new JsonWriterOptions { Encoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping }))
+            {
+                w.WriteStartObject();
+                w.WriteString("url"u8, url);
+                w.WriteString("action"u8, "redirect"u8);
+                if (replace)
+                    w.WriteBoolean("replace"u8, true);
+                if (allowSpa)
+                    w.WriteBoolean("allowSpa"u8, true);
+                if (downloadName is not null)
+                    w.WriteString("download"u8, downloadName);
+                w.WriteEndObject();
+            }
+            return result.ToArray();
         }
 
         /// <summary>
@@ -355,8 +366,7 @@ public static string GenerateRedirectActionResponse(string url, bool replace, bo
         /// </summary>
         internal static string GenerateMissingCachedViewModelResponse()
         {
-            // create result object
-            return JsonSerializer.Serialize(new { action = "viewModelNotCached" }, DefaultSerializerSettingsProvider.Instance.SettingsHtmlUnsafe);
+            return """{"action":"viewModelNotCached"}""";
         }
 
         /// <summary>