diff --git a/src/systems/si/include/units/isq/si/luminous_flux.h b/src/systems/si/include/units/isq/si/luminous_flux.h
index 7d9592e3..f2b30290 100644
--- a/src/systems/si/include/units/isq/si/luminous_flux.h
+++ b/src/systems/si/include/units/isq/si/luminous_flux.h
@@ -36,7 +36,7 @@ namespace units::isq::si {
 
 // TODO Is this correct? Should we account for steradian here? How?
 
-struct lumen : named_scaled_unit<lumen, "lm", ratio(1, 683), watt> {};
+struct lumen : named_scaled_unit<lumen, "lm", as_magnitude<ratio(1, 683)>(), watt> {};
 
 using dim_luminous_flux = dim_power;