diff --git a/mpcontribs-client/mpcontribs/client/__init__.py b/mpcontribs-client/mpcontribs/client/__init__.py
index 772b0f578..613698100 100644
--- a/mpcontribs-client/mpcontribs/client/__init__.py
+++ b/mpcontribs-client/mpcontribs/client/__init__.py
@@ -1517,15 +1517,25 @@ def init_columns(self, columns: dict = None) -> dict:
                     new_unit = new_column.get("unit", "NaN")
                     existing_unit = existing_column.get("unit")
                     if existing_unit != new_unit:
+                        conv_args = []
+                        for u in [existing_unit, new_unit]:
+                            try:
+                                conv_args.append(ureg.Unit(u))
+                            except ValueError as ex:
+                                raise MPContribsClientError(
+                                    f"Can't convert {existing_unit} to {new_unit} for {path}"
+                                )
                         try:
-                            factor = ureg.convert(1, ureg.Unit(existing_unit), ureg.Unit(new_unit))
+                            factor = ureg.convert(1, *conv_args)
                         except DimensionalityError:
                             raise MPContribsClientError(
                                 f"Can't convert {existing_unit} to {new_unit} for {path}"
                             )
 
                         if not isclose(factor, 1):
-                            logger.info(f"Changing {existing_unit} to {new_unit} for {path} ...")
+                            logger.info(
+                                f"Changing {existing_unit} to {new_unit} for {path} ..."
+                            )
                             # TODO scale contributions to new unit
                             raise MPContribsClientError(
                                 "Changing units not supported yet. Please resubmit"