diff --git a/lib/microwaveprop_web/live/path_live.ex b/lib/microwaveprop_web/live/path_live.ex
index 4592b099..4161bfce 100644
--- a/lib/microwaveprop_web/live/path_live.ex
+++ b/lib/microwaveprop_web/live/path_live.ex
@@ -380,7 +380,9 @@ defmodule MicrowavepropWeb.PathLive do
 
     diffraction_loss =
       if terrain_result do
-        terrain_result.analysis.diffraction_db
+        # TerrainAnalysis.deygout_diffraction returns integer 0 for clear
+        # paths; coerce to float so Float.round/2 below is happy.
+        terrain_result.analysis.diffraction_db * 1.0
       else
         0.0
       end