diff --git a/.chronus/changes/HEAD-2025-11-16-13-29-48.md b/.chronus/changes/HEAD-2025-11-16-13-29-48.md
new file mode 100644
index 00000000000..1d38a28a02a
--- /dev/null
+++ b/.chronus/changes/HEAD-2025-11-16-13-29-48.md
@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/http-client-python"
+---
+
+fix client default value for special headers
\ No newline at end of file
diff --git a/packages/http-client-python/generator/pygen/codegen/serializers/builder_serializer.py b/packages/http-client-python/generator/pygen/codegen/serializers/builder_serializer.py
index ef61ff347cc..d5db45a3294 100644
--- a/packages/http-client-python/generator/pygen/codegen/serializers/builder_serializer.py
+++ b/packages/http-client-python/generator/pygen/codegen/serializers/builder_serializer.py
@@ -403,7 +403,12 @@ def declare_non_inputtable_headers_queries(
         builder: RequestBuilderType,
     ) -> list[str]:
         def _get_value(param):
-            declaration = param.get_declaration() if param.constant else None
+            if param.constant:
+                declaration = param.get_declaration()
+            elif param.client_default_value_declaration is not None:
+                declaration = param.client_default_value_declaration
+            else:
+                declaration = None
             if param.location in [ParameterLocation.HEADER, ParameterLocation.QUERY]:
                 kwarg_dict = "headers" if param.location == ParameterLocation.HEADER else "params"
                 return f"_{kwarg_dict}.pop('{param.wire_name}', {declaration})"