diff --git a/BuildingCoder/BuildingCoder/Util.cs b/BuildingCoder/BuildingCoder/Util.cs
index 679a25f9..20b57edd 100644
--- a/BuildingCoder/BuildingCoder/Util.cs
+++ b/BuildingCoder/BuildingCoder/Util.cs
@@ -236,7 +236,7 @@ public static double Max( double[] a )
     /// </summary>
     public static XYZ Midpoint( XYZ p, XYZ q )
     {
-      return p + 0.5 * ( q - p );
+      return 0.5 * ( p + q );
     }
 
     /// <summary>