diff --git a/src/core/Geometry.js b/src/core/Geometry.js
index 200db07b5b1286d304d9e97288569ff86bc6c0bd..e1bef6a42bf9ae46bcb0b77f6e66386a0724f21b 100644
--- a/src/core/Geometry.js
+++ b/src/core/Geometry.js
@@ -258,12 +258,12 @@ THREE.Geometry.prototype = {
 
 		}
 
-		function addFace( a, b, c ) {
+		function addFace( a, b, c, materialIndex ) {
 
 			var vertexNormals = normals !== undefined ? [ tempNormals[ a ].clone(), tempNormals[ b ].clone(), tempNormals[ c ].clone() ] : [];
 			var vertexColors = colors !== undefined ? [ scope.colors[ a ].clone(), scope.colors[ b ].clone(), scope.colors[ c ].clone() ] : [];
 
-			var face = new THREE.Face3( a, b, c, vertexNormals, vertexColors );
+			var face = new THREE.Face3( a, b, c, vertexNormals, vertexColors, materialIndex );
 
 			scope.faces.push( face );
 
@@ -296,7 +296,7 @@ THREE.Geometry.prototype = {
 
 					for ( var j = start, jl = start + count; j < jl; j += 3 ) {
 
-						addFace( indices[ j ], indices[ j + 1 ], indices[ j + 2 ] );
+						addFace( indices[ j ], indices[ j + 1 ], indices[ j + 2 ], group.materialIndex  );
 
 					}