diff --git a/units/src/lib.rs b/units/src/lib.rs
index 84f946df..85b7bb46 100644
--- a/units/src/lib.rs
+++ b/units/src/lib.rs
@@ -33,28 +33,6 @@ pub type InvertDimension<D> = uom::si::ISQ<
 /// metres and seconds as the base units of `Length` and `Time`
 /// Useful for bitwise compatibility with data generated by Geant4.
 pub mod mmps {
-
-  use uom::si::{
-    length::millimeter,
-    mass::kilogram,
-    time::picosecond,
-    electric_current::ampere,
-    thermodynamic_temperature::kelvin,
-    amount_of_substance::mole,
-    luminous_intensity::candela,
-  };
-
-  // TODO: replace with system! macro, once it has been fixed in uom
-  pub type Units = dyn uom::si::Units<
-      f32,
-    length                    = millimeter,
-    mass                      = kilogram,
-    time                      = picosecond,
-    electric_current          = ampere,
-    thermodynamic_temperature = kelvin,
-    amount_of_substance       = mole,
-    luminous_intensity        = candela>;
-
   pub mod f32 {
     use uom::{ISQ, system};
     ISQ!(uom::si, f32, (millimeter, kilogram, picosecond, ampere, kelvin, mole, candela));
@@ -80,8 +58,8 @@ pub mod mmps {
 }
 
 use uom::typenum::{P2, N1, Z0};
-pub type PerLength   = Quantity<InvertDimension<uom::si::length::Dimension>, mmps::Units, f32>;
-pub type AreaPerMass = Quantity<uom::si::ISQ<P2, N1, Z0, Z0, Z0, Z0, Z0>   , mmps::Units, f32>;
+pub type PerLength   = Quantity<InvertDimension<uom::si::length::Dimension>, mmps::f32::Units, f32>;
+pub type AreaPerMass = Quantity<uom::si::ISQ<P2, N1, Z0, Z0, Z0, Z0, Z0>   , mmps::f32::Units, f32>;
 
 //use uom::fmt::DisplayStyle::Abbreviation;
 pub use uom::si::Quantity;