diff --git a/rust/prop_grid_rs/src/weather_scalar_file.rs b/rust/prop_grid_rs/src/weather_scalar_file.rs
index 37242cdb..9025d181 100644
--- a/rust/prop_grid_rs/src/weather_scalar_file.rs
+++ b/rust/prop_grid_rs/src/weather_scalar_file.rs
@@ -309,7 +309,7 @@ fn compute_lapse_rate(sorted: &[&Level]) -> Option<f64> {
 }
 
 fn compute_layer_lapse_rate(sorted: &[&Level], lower_pres: f64, upper_pres: f64) -> Option<f64> {
-    if !(lower_pres > upper_pres) {
+    if lower_pres <= upper_pres {
         return None;
     }
     let lower = sorted