diff --git a/src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIJsonSerializerContext.cs b/src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIJsonSerializerContext.cs
index ed15c9df84..72e175fb6e 100644
--- a/src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIJsonSerializerContext.cs
+++ b/src/Swashbuckle.AspNetCore.SwaggerUI/SwaggerUIJsonSerializerContext.cs
@@ -1,4 +1,7 @@
 #if NET6_0_OR_GREATER
+using System;
+using System.Text.Json;
+using System.Text.Json.Nodes;
 using System.Text.Json.Serialization;
 
 namespace Swashbuckle.AspNetCore.SwaggerUI;
@@ -6,6 +9,36 @@ namespace Swashbuckle.AspNetCore.SwaggerUI;
 [JsonSerializable(typeof(ConfigObject))]
 [JsonSerializable(typeof(InterceptorFunctions))]
 [JsonSerializable(typeof(OAuthConfigObject))]
+// These primitive types are declared for common types that may be used with ConfigObject.AdditionalItems. See https://github.com/domaindrivendev/Swashbuckle.AspNetCore/issues/2884.
+[JsonSerializable(typeof(bool))]
+[JsonSerializable(typeof(byte))]
+[JsonSerializable(typeof(sbyte))]
+[JsonSerializable(typeof(short))]
+[JsonSerializable(typeof(ushort))]
+[JsonSerializable(typeof(int))]
+[JsonSerializable(typeof(uint))]
+[JsonSerializable(typeof(long))]
+[JsonSerializable(typeof(ulong))]
+[JsonSerializable(typeof(float))]
+[JsonSerializable(typeof(double))]
+[JsonSerializable(typeof(decimal))]
+[JsonSerializable(typeof(char))]
+[JsonSerializable(typeof(string))]
+[JsonSerializable(typeof(DateTime))]
+[JsonSerializable(typeof(DateTimeOffset))]
+[JsonSerializable(typeof(TimeSpan))]
+[JsonSerializable(typeof(JsonArray))]
+[JsonSerializable(typeof(JsonObject))]
+[JsonSerializable(typeof(JsonDocument))]
+#if NET7_0_OR_GREATER
+[JsonSerializable(typeof(DateOnly))]
+[JsonSerializable(typeof(TimeOnly))]
+#endif
+#if NET8_0_OR_GREATER
+[JsonSerializable(typeof(Half))]
+[JsonSerializable(typeof(Int128))]
+[JsonSerializable(typeof(UInt128))]
+#endif
 [JsonSourceGenerationOptions(
     DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
     PropertyNamingPolicy = JsonKnownNamingPolicy.CamelCase)]
diff --git a/test/WebSites/CustomUIConfig/Startup.cs b/test/WebSites/CustomUIConfig/Startup.cs
index 9a86e2dced..abfefe10dc 100644
--- a/test/WebSites/CustomUIConfig/Startup.cs
+++ b/test/WebSites/CustomUIConfig/Startup.cs
@@ -1,9 +1,11 @@
+using System;
+using System.Text.Json;
+using System.Text.Json.Nodes;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
-using Microsoft.OpenApi.Models;
 using Swashbuckle.AspNetCore.SwaggerUI;
 
 namespace CustomUIConfig
@@ -76,6 +78,34 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
                 c.UseResponseInterceptor("(res) => { console.log('Custom interceptor intercepted response from:', res.url); return res; }");
                 c.EnablePersistAuthorization();
 
+                c.ConfigObject.AdditionalItems.Add("syntaxHighlight", false);
+                c.ConfigObject.AdditionalItems.Add("charProperty", 'c');
+                c.ConfigObject.AdditionalItems.Add("stringProperty", "value");
+                c.ConfigObject.AdditionalItems.Add("byteProperty", (byte)1);
+                c.ConfigObject.AdditionalItems.Add("signedByteProperty", (sbyte)1);
+                c.ConfigObject.AdditionalItems.Add("int16Property", (short)1);
+                c.ConfigObject.AdditionalItems.Add("uint16Property", (ushort)1);
+                c.ConfigObject.AdditionalItems.Add("int32Property", 1);
+                c.ConfigObject.AdditionalItems.Add("uint32Property", 1u);
+                c.ConfigObject.AdditionalItems.Add("int64Property", 1L);
+                c.ConfigObject.AdditionalItems.Add("uint64Property", 1uL);
+                c.ConfigObject.AdditionalItems.Add("floatProperty", 1f);
+                c.ConfigObject.AdditionalItems.Add("doubleProperty", 1d);
+                c.ConfigObject.AdditionalItems.Add("decimalProperty", 1m);
+                c.ConfigObject.AdditionalItems.Add("dateTimeProperty", DateTime.UtcNow);
+                c.ConfigObject.AdditionalItems.Add("dateTimeOffsetProperty", DateTimeOffset.UtcNow);
+                c.ConfigObject.AdditionalItems.Add("timeSpanProperty", new TimeSpan(12, 34, 56));
+                c.ConfigObject.AdditionalItems.Add("jsonArray", new JsonArray() { "string" });
+                c.ConfigObject.AdditionalItems.Add("jsonObject", new JsonObject() { ["foo"] = "bar" });
+                c.ConfigObject.AdditionalItems.Add("jsonDocument", JsonDocument.Parse("""{ "foo": "bar" }"""));
+
+#if NET8_0_OR_GREATER
+                c.ConfigObject.AdditionalItems.Add("dateOnlyProperty", new DateOnly(1977, 05, 25));
+                c.ConfigObject.AdditionalItems.Add("timeOnlyProperty", new TimeOnly(12, 34, 56));
+                c.ConfigObject.AdditionalItems.Add("halfProperty", Half.CreateChecked(1));
+                c.ConfigObject.AdditionalItems.Add("int128Property", Int128.CreateChecked(1));
+                c.ConfigObject.AdditionalItems.Add("unt128Property", UInt128.CreateChecked(1));
+#endif
             });
         }
     }