diff --git a/lib/xmet/thermo.py b/lib/xmet/thermo.py
index 1c17ec0..3903c87 100644
--- a/lib/xmet/thermo.py
+++ b/lib/xmet/thermo.py
@@ -129,9 +129,7 @@ def loft_parcel(start_temp: float,
             except OverflowError:
                 break
 
-            height_delta = height - height_last
-
-            temp = lapse(temp, height_delta, rate)
+            temp = lapse(temp, height - height_last, rate)
 
             yield temp, pressure