diff --git a/scripts/RmAdjustStorageCapacity.lua b/scripts/RmAdjustStorageCapacity.lua
index c2350a8..0583d15 100644
--- a/scripts/RmAdjustStorageCapacity.lua
+++ b/scripts/RmAdjustStorageCapacity.lua
@@ -1940,11 +1940,15 @@ function RmAdjustStorageCapacity:applyVehicleCapacity(vehicle, fillUnitIndex, ca
 
     -- Apply proportional discharge speed
     local spec = vehicle[RmVehicleStorageCapacity.SPEC_TABLE_NAME]
-    if spec ~= nil and spec.applyProportionalDischargeSpeed ~= nil then
-        -- Call via method on the vehicle/spec
+    if spec ~= nil then
         RmVehicleStorageCapacity.applyProportionalDischargeSpeed(vehicle, fillUnitIndex, capacity)
     end
 
+    -- Capacity affects the additional-mass calculation, so discard the cached value.
+    if vehicle.setMassDirty ~= nil then
+        vehicle:setMassDirty()
+    end
+
     -- Update FillVolume cached capacity for visual representation
     self:updateVehicleFillVolumeCapacity(vehicle, fillUnitIndex, capacity)
 end