diff --git a/api/src/opentrons/protocol_api/module_contexts.py b/api/src/opentrons/protocol_api/module_contexts.py
index a277403612e..7e8cc60a1f2 100644
--- a/api/src/opentrons/protocol_api/module_contexts.py
+++ b/api/src/opentrons/protocol_api/module_contexts.py
@@ -1162,6 +1162,8 @@ def retrieve(self) -> Labware:
         """Release and return a labware at the bottom of the labware stack."""
         self._core.retrieve()
         labware_core = self._protocol_core.get_labware_on_module(self._core)
+        # the core retrieve command should have already raised the error
+        # if labware_core is None, this is just to satisfy the type checker
         assert labware_core is not None, "Retrieve failed to return labware"
         # check core map first
         try: