diff --git a/examples/js/exporters/GLTFExporter.js b/examples/js/exporters/GLTFExporter.js
index 8a7c37eb8113661da6a424424bc3377e46ba2eb3..2f6a337cbe07b7ff2ea95144c3f62f51a348aca1 100644
--- a/examples/js/exporters/GLTFExporter.js
+++ b/examples/js/exporters/GLTFExporter.js
@@ -396,7 +396,7 @@ THREE.GLTFExporter.prototype = {
 		 */
 		function processImage( map ) {
 
-			if ( cachedData.images[ map.uuid ] ) {
+			if ( cachedData.images[ map.uuid ] !== undefined ) {
 
 				return cachedData.images[ map.uuid ];
 
@@ -507,7 +507,7 @@ THREE.GLTFExporter.prototype = {
 		 */
 		function processMaterial( material ) {
 
-			if ( cachedData.materials[ material.uuid ] ) {
+			if ( cachedData.materials[ material.uuid ] !== undefined ) {
 
 				return cachedData.materials[ material.uuid ];