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 9ff0fba72d0..bda2ce4efa7 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
@@ -104,7 +104,7 @@ defmodule {{moduleName}}.RequestBuilder do
     headers =
       request
       |> Map.get(:headers, [])
-      |> List.keystore(key, 0, {key, value})
+      |> List.keystore(to_string(key), 0, {to_string(key), to_string(value)})
 
     Map.put(request, :headers, headers)
   end
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 987ac303f50..601777acafc 100644
--- a/samples/client/petstore/elixir/lib/openapi_petstore/request_builder.ex
+++ b/samples/client/petstore/elixir/lib/openapi_petstore/request_builder.ex
@@ -106,7 +106,7 @@ defmodule OpenapiPetstore.RequestBuilder do
     headers =
       request
       |> Map.get(:headers, [])
-      |> List.keystore(key, 0, {key, value})
+      |> List.keystore(to_string(key), 0, {to_string(key), to_string(value)})
 
     Map.put(request, :headers, headers)
   end