diff --git a/lib/openai/internal/type/base_model.rb b/lib/openai/internal/type/base_model.rb
index d7dade74..1f4f669f 100644
--- a/lib/openai/internal/type/base_model.rb
+++ b/lib/openai/internal/type/base_model.rb
@@ -258,6 +258,7 @@ def dump(value)
               return super
             end
 
+            is_param = singleton_class <= OpenAI::Internal::Type::RequestParameters::Converter
             acc = {}
 
             coerced.each do |key, val|
@@ -266,19 +267,21 @@ def dump(value)
               in nil
                 acc.store(name, super(val))
               else
-                mode, api_name, type_fn = field.fetch_values(:mode, :api_name, :type_fn)
+                mode, type_fn = field.fetch_values(:mode, :type_fn)
                 case mode
                 in :coerce
                   next
                 else
                   target = type_fn.call
+                  api_name = is_param ? name : field.fetch(:api_name)
                   acc.store(api_name, OpenAI::Internal::Type::Converter.dump(target, val))
                 end
               end
             end
 
-            known_fields.each_value do |field|
-              mode, api_name, const = field.fetch_values(:mode, :api_name, :const)
+            known_fields.each do |name, field|
+              mode, const = field.fetch_values(:mode, :const)
+              api_name = is_param ? name : field.fetch(:api_name)
               next if mode == :coerce || acc.key?(api_name) || const == OpenAI::Internal::OMIT
               acc.store(api_name, const)
             end
diff --git a/lib/openai/resources/fine_tuning/jobs.rb b/lib/openai/resources/fine_tuning/jobs.rb
index 8e28f8c7..8032932a 100644
--- a/lib/openai/resources/fine_tuning/jobs.rb
+++ b/lib/openai/resources/fine_tuning/jobs.rb
@@ -36,7 +36,7 @@ def create(params)
           @client.request(
             method: :post,
             path: "fine_tuning/jobs",
-            body: parsed,
+            body: parsed.transform_keys(method_: :method),
             model: OpenAI::Models::FineTuning::FineTuningJob,
             options: options
           )