diff --git a/src/include/units/physical/si/mass.h b/src/include/units/physical/si/mass.h
index 4f8b6a56..2a22a0b0 100644
--- a/src/include/units/physical/si/mass.h
+++ b/src/include/units/physical/si/mass.h
@@ -30,7 +30,7 @@ namespace units::si {
 
 struct gram : named_unit<gram, "g", prefix> {};
 struct kilogram : prefixed_unit<kilogram, kilo, gram> {};
-struct tonne : named_scaled_unit<tonne, "t", prefix, ratio<1'0000>, kilogram> {};
+struct tonne : named_scaled_unit<tonne, "t", prefix, ratio<1'000>, kilogram> {};
 
 struct dim_mass : physical::dim_mass<kilogram> {};