# sympy__sympy-24213
# Loki Mode Multi-Agent Patch
# Attempts: 1

Based on the architect's analysis and the error message in the issue, I can generate the patch. The issue is clear: in the `Add` handling block, there's a direct comparison `if dim != addend_dim:` that should be replaced with a call to `equivalent_dims` to check physical equivalence.

--- a/sympy/physics/units/unitsystem.py
+++ b/sympy/physics/units/unitsystem.py
@@ -174,7 +174,7 @@ class UnitSystem(_QuantityMapper):
                 addend_factor, addend_dim = \
                     self._collect_factor_and_dimension(addend)
                 if dim != addend_dim:
-                    raise ValueError(
+                    if not self.get_dimension_system().equivalent_dims(dim, addend_dim):
+                        raise ValueError(
                         'Dimension of "{}" is {}, '
                         'but it should be {}'.format(
                             addend, addend_dim, dim))