diff --git a/modules/openapi-generator/src/main/resources/elixir/request_builder.ex.mustache b/modules/openapi-generator/src/main/resources/elixir/request_builder.ex.mustache
index 825beac5a43..6da43f8eddc 100644
--- a/modules/openapi-generator/src/main/resources/elixir/request_builder.ex.mustache
+++ b/modules/openapi-generator/src/main/resources/elixir/request_builder.ex.mustache
@@ -101,7 +101,12 @@ defmodule {{moduleName}}.RequestBuilder do
   end
 
   def add_param(request, :headers, key, value) do
-    Tesla.put_header(request, key, value)
+    headers =
+      request
+      |> Map.get(:headers, [])
+      |> List.keystore(key, 0, {key, value})
+
+    Map.put(request, :headers, headers)
   end
 
   def add_param(request, :file, name, path) do
diff --git a/samples/client/petstore/elixir/lib/openapi_petstore/request_builder.ex b/samples/client/petstore/elixir/lib/openapi_petstore/request_builder.ex
index 97b0e434acd..8b6b1a70bf4 100644
--- a/samples/client/petstore/elixir/lib/openapi_petstore/request_builder.ex
+++ b/samples/client/petstore/elixir/lib/openapi_petstore/request_builder.ex
@@ -103,7 +103,12 @@ defmodule OpenapiPetstore.RequestBuilder do
   end
 
   def add_param(request, :headers, key, value) do
-    Tesla.put_header(request, key, value)
+    headers =
+      request
+      |> Map.get(:headers, [])
+      |> List.keystore(key, 0, {key, value})
+
+    Map.put(request, :headers, headers)
   end
 
   def add_param(request, :file, name, path) do