diff --git a/flytekit/image_spec/default_builder.py b/flytekit/image_spec/default_builder.py
index 760c845cd2..09b874693e 100644
--- a/flytekit/image_spec/default_builder.py
+++ b/flytekit/image_spec/default_builder.py
@@ -244,6 +244,7 @@ class DefaultImageBuilder(ImageSpecBuilder):
         "cudnn",
         "base_image",
         "pip_index",
+        "pip_extra_index_url",
         # "registry_config",
         "commands",
     }