diff --git a/src/Slicer.js b/src/Slicer.js
index 08106a8..a0a7069 100644
--- a/src/Slicer.js
+++ b/src/Slicer.js
@@ -23,9 +23,6 @@ export default class {
       geometry.applyMatrix(matrix);
     }
 
-    geometry.mergeVertices();
-    geometry.computeFaceNormals();
-
     this.geometry = geometry;
 
     return this;
diff --git a/src/sliceActions/slice.js b/src/sliceActions/slice.js
index 8ee13b9..2b3f47f 100644
--- a/src/sliceActions/slice.js
+++ b/src/sliceActions/slice.js
@@ -13,6 +13,9 @@ import applyPrecision from './applyPrecision.js';
 import removePrecision from './removePrecision.js';
 
 export default function(geometry, settings) {
+  geometry.mergeVertices();
+  geometry.computeFaceNormals();
+
   // get unique lines from geometry;
   const openClosed = detectOpenClosed(geometry);
   const lines = createLines(geometry, settings, openClosed);