diff --git a/builder/py/orchestrate.py b/builder/py/orchestrate.py
index 9767c44..c5130be 100644
--- a/builder/py/orchestrate.py
+++ b/builder/py/orchestrate.py
@@ -200,7 +200,7 @@ class Orchestrator:
         stage = resolve_module_docker_override(self.root, kind, name, phase)
         if not stage:
             return None
-        return RuntimeConfig(stage.image, stage.dockerfile, stage.docker_context or ".")
+        return RuntimeConfig(stage.image or "", stage.dockerfile or "", stage.docker_context or ".")
 
     def run_python(self, kind: str, name: str, phase: str, *, profile_name: str = "", base_name: str = "", feature_name: str = "") -> None:
         module_dir = (base_dir if kind == "base" else feature_dir)(self.root, name)