diff --git a/setuptools/command/editable_wheel.py b/setuptools/command/editable_wheel.py
index 1a544ec258..3a247ce4ff 100644
--- a/setuptools/command/editable_wheel.py
+++ b/setuptools/command/editable_wheel.py
@@ -836,6 +836,11 @@ def _find_spec(cls, fullname: str, candidate_path: Path) -> ModuleSpec | None:
         for candidate in chain([init], candidates):
             if candidate.exists():
                 return spec_from_file_location(fullname, candidate)
+        if candidate_path.is_dir():
+            # treat it like a PEP 420 namespace package
+            spec = ModuleSpec(fullname, None, is_package=True)
+            spec.submodule_search_locations = [str(candidate_path)]
+            return spec
         return None