diff --git a/KeepersCompound.Lightmapper/PotentiallyVisibleSet.cs b/KeepersCompound.Lightmapper/PotentiallyVisibleSet.cs
index 514530d..5ea39a4 100644
--- a/KeepersCompound.Lightmapper/PotentiallyVisibleSet.cs
+++ b/KeepersCompound.Lightmapper/PotentiallyVisibleSet.cs
@@ -163,7 +163,7 @@ public class PotentiallyVisibleSet
                 var validTarget = false;
                 foreach (var v in target.Poly.Vertices)
                 {
-                    if (MathUtils.DistanceFromPlane(sourcePlane, v) < -MathUtils.Epsilon)
+                    if (MathUtils.DistanceFromNormalizedPlane(sourcePlane, v) < -MathUtils.Epsilon)
                     {
                         validTarget = true;
                         break;
@@ -178,7 +178,7 @@ public class PotentiallyVisibleSet
                 validTarget = false;
                 foreach (var v in source.Poly.Vertices)
                 {
-                    if (MathUtils.DistanceFromPlane(targetPlane, v) > MathUtils.Epsilon)
+                    if (MathUtils.DistanceFromNormalizedPlane(targetPlane, v) > MathUtils.Epsilon)
                     {
                         validTarget = true;
                         break;
diff --git a/KeepersCompound.Lightmapper/Utils.cs b/KeepersCompound.Lightmapper/Utils.cs
index c3b8e29..5739aad 100644
--- a/KeepersCompound.Lightmapper/Utils.cs
+++ b/KeepersCompound.Lightmapper/Utils.cs
@@ -93,6 +93,11 @@ public static class MathUtils
         return (Vector3.Dot(plane.Normal, point) + plane.D) / plane.Normal.Length();
     }
     
+    public static float DistanceFromNormalizedPlane(Plane plane, Vector3 point)
+    {
+        return Vector3.Dot(plane.Normal, point) + plane.D;
+    }
+    
     public static bool IsCoplanar(Plane p0, Plane p1)
     {
         var m = p0.D / p1.D;