diff --git a/cara/models.py b/cara/models.py
index 2032aff2..7addbaa8 100644
--- a/cara/models.py
+++ b/cara/models.py
@@ -1032,7 +1032,7 @@ class ConcentrationModel:
         Note that time is not vectorised. You can only pass a single float
         to this method.
         """
-        return (self._normed_concentration(time) * 
+        return (self._normed_concentration_cached(time) * 
                 self.infected.emission_rate_when_present())
 
     @method_cache