diff --git a/src/DigitalData.Swagger.Proxy/Configs/OriginServerParams.cs b/src/DigitalData.Swagger.Proxy/Configs/OriginServerParams.cs
index 7851bdc..9c3546e 100644
--- a/src/DigitalData.Swagger.Proxy/Configs/OriginServerParams.cs
+++ b/src/DigitalData.Swagger.Proxy/Configs/OriginServerParams.cs
@@ -4,6 +4,6 @@
     {
         public required string Url { get; init; }
 
-        public Dictionary<string, string>? DefaultHeaders { get; init; }
+        public Dictionary<string, string> DefaultHeaders { get; init; } = new();
     }
 }
\ No newline at end of file
diff --git a/src/DigitalData.Swagger.Proxy/Controllers/ProxyController.cs b/src/DigitalData.Swagger.Proxy/Controllers/ProxyController.cs
index c78d96d..2c68ca8 100644
--- a/src/DigitalData.Swagger.Proxy/Controllers/ProxyController.cs
+++ b/src/DigitalData.Swagger.Proxy/Controllers/ProxyController.cs
@@ -11,12 +11,12 @@ using System.Threading.Tasks;
 [ApiController]
 public class ProxyController(IOptions<OriginServerParams> originServerParamsOptions) : ControllerBase
 {
-    private readonly OriginServerParams origin = originServerParamsOptions.Value;
+    private readonly OriginServerParams _origin = originServerParamsOptions.Value;
 
     [HttpPost("{servicetierName}/ODataV4/{webserviceName}_CreateInvoice")]
     public async Task<IActionResult> Redir([FromRoute] string servicetierName, [FromRoute] string webserviceName, [FromQuery] string company)
     {
-        var res = await origin.Url
+        var res = await _origin.Url
             .AppendPathSegment(servicetierName)
             .AppendPathSegment("ODataV4")
             .AppendPathSegment(webserviceName + "_CreateInvoice")
@@ -24,9 +24,14 @@ public class ProxyController(IOptions<OriginServerParams> originServerParamsOpti
             //.WithOAuthBearerToken("my_oauth_token")
             .PostAsync();
 
+        //merge with default headers
+        var mergedDictionary = _origin.DefaultHeaders
+            .Concat(res.Headers.ToDictionary(kv => kv.Name, kv => kv.Value))
+            .ToDictionary(kv => kv.Key, kv => kv.Value);
+        
         // set headers
-        foreach (var (Name, Value) in res.Headers)
-            HttpContext.Response.Headers[Name] = Value;
+        foreach (var header in mergedDictionary)
+            HttpContext.Response.Headers[header.Key] = header.Value;
 
         // set cookies
         foreach (var (Name, Value) in res.Cookies.ToKeyValuePairs())
diff --git a/src/DigitalData.Swagger.Proxy/appsettings.json b/src/DigitalData.Swagger.Proxy/appsettings.json
index b9d7a31..6dd8d2c 100644
--- a/src/DigitalData.Swagger.Proxy/appsettings.json
+++ b/src/DigitalData.Swagger.Proxy/appsettings.json
@@ -9,7 +9,7 @@
   "OriginServer": {
     "Url": "https://localhost:7248",
     "DefaultHeaders": {
-
+      "foo": "bar"
     }
   }
 }