diff --git a/arbor/include/arbor/units.hpp b/arbor/include/arbor/units.hpp
index c361209a5..b7be90b7b 100644
--- a/arbor/include/arbor/units.hpp
+++ b/arbor/include/arbor/units.hpp
@@ -82,7 +82,8 @@ constexpr inline auto C = ::units::precise::coulomb;
 
 // mol and molarity
 using ::units::precise::mol;
-constexpr inline auto M = mol / m.pow(3);
+using ::units::precise::L;
+constexpr inline auto M = mol / L;
 constexpr inline auto mM = milli * M;
 
 using ::units::is_valid;