diff --git a/src/voxel_mesh.ts b/src/voxel_mesh.ts
index a13a360..a3f6b2e 100644
--- a/src/voxel_mesh.ts
+++ b/src/voxel_mesh.ts
@@ -87,12 +87,14 @@ export class VoxelMesh {
         const pos = inPos.copy().round();
         const voxel = this._voxels.get(pos.hash());
 
-        if (voxel !== undefined && this._voxelMeshParams.voxelOverlapRule === 'average') {
-            voxel.colour.r = ((voxel.colour.r * voxel.collisions) + colour.r) / (voxel.collisions + 1);
-            voxel.colour.g = ((voxel.colour.g * voxel.collisions) + colour.g) / (voxel.collisions + 1);
-            voxel.colour.b = ((voxel.colour.b * voxel.collisions) + colour.b) / (voxel.collisions + 1);
-            voxel.colour.a = ((voxel.colour.a * voxel.collisions) + colour.a) / (voxel.collisions + 1);
-            ++voxel.collisions;
+        if (voxel !== undefined) {
+            if (this._voxelMeshParams.voxelOverlapRule === 'average') {
+                voxel.colour.r = ((voxel.colour.r * voxel.collisions) + colour.r) / (voxel.collisions + 1);
+                voxel.colour.g = ((voxel.colour.g * voxel.collisions) + colour.g) / (voxel.collisions + 1);
+                voxel.colour.b = ((voxel.colour.b * voxel.collisions) + colour.b) / (voxel.collisions + 1);
+                voxel.colour.a = ((voxel.colour.a * voxel.collisions) + colour.a) / (voxel.collisions + 1);
+                ++voxel.collisions;
+            }
         } else {
             this._voxels.set(pos.hash(), {
                 position: pos,