diff --git a/lib/addDefaults.js b/lib/addDefaults.js
index 5022e152..07aa091e 100644
--- a/lib/addDefaults.js
+++ b/lib/addDefaults.js
@@ -44,7 +44,7 @@ function animationDefaults(gltf) {
                 animation.samplers = {};
             }
 
-            var samplers = animations.samplers;
+            var samplers = animation.samplers;
 
             for (var samplerName in samplers) {
                 if (samplers.hasOwnProperty(samplerName)) {
@@ -72,6 +72,7 @@ function assetDefaults(gltf) {
     profile.api = defaultValue(profile.api, 'WebGL');
     profile.version = defaultValue(profile.version, '1.0.2');
 
+    // glTF 0.8 backward compatibility
     if (defined(gltf.version)) {
         asset.version = defaultValue(asset.version, gltf.version);
         delete gltf.version;
@@ -113,6 +114,7 @@ function imageDefaults(gltf) {
     }
 }
 
+// TODO: move lightDefaults() for KHR_materials_common elsewhere?
 function lightDefaults(gltf) {
     if (!defined(gltf.extensions)) {
         gltf.extensions = {};
@@ -125,6 +127,7 @@ function lightDefaults(gltf) {
     var khrMaterialsCommon = extensions.KHR_materials_common;
 
     if (defined(gltf.lights)) {
+        // glTF 0.8 backward compatibility
         khrMaterialsCommon.lights = gltf.lights;
         delete gltf.lights;
     }
@@ -198,6 +201,7 @@ function materialDefaults(gltf) {
             var material = materials[name];
             var instanceTechnique = material.instanceTechnique;
             if (defined(instanceTechnique)) {
+                // glTF 0.8 backward compatibility
                 material.technique = instanceTechnique.technique;
                 material.values = instanceTechnique.values;
 
@@ -255,7 +259,7 @@ function meshDefaults(gltf) {
                 mesh.primitives = [];
             }
 
-            var primitives = mesh.primitives.length;
+            var primitives = mesh.primitives;
             var length = primitives.length;
             for (var i = 0; i < length; ++i) {
                 var primitive = primitives[i];
@@ -266,7 +270,6 @@ function meshDefaults(gltf) {
 
                 // Backwards compatibility for glTF 0.8. primitive was renamed to mode.
                 var defaultMode = defaultValue(primitive.primitive, WebGLConstants.TRIANGLES);
-
                 primitive.mode = defaultValue(primitive.mode, defaultMode);
             }
         }
@@ -291,6 +294,7 @@ function nodeDefaults(gltf) {
             }
 
             if (hasAxisAngle && defined(node.rotation)) {
+                // glTF 0.8 backward compatibility
                 var rotation = node.rotation;
                 Cartesian3.fromArray(rotation, 0, axis);
                 Quaternion.fromAxisAngle(axis, rotation[3], quat);
@@ -374,8 +378,8 @@ function sceneDefaults(gltf) {
     for (var name in scenes) {
         if (scenes.hasOwnProperty(name)) {
             var scene = scenes[name];
-            if (!defined(scene.node)) {
-                scene.node = [];
+            if (!defined(scene.nodes)) {
+                scene.nodes = [];
             }
         }
     }
@@ -396,7 +400,7 @@ function skinDefaults(gltf) {
     for (var name in skins) {
         if (skins.hasOwnProperty(name)) {
             var skin = skins[name];
-            if (defined(skin.bindShapeMatrix)) {
+            if (!defined(skin.bindShapeMatrix)) {
                 skin.bindShapeMatrix = [
                     1.0, 0.0, 0.0, 0.0,
                     0.0, 1.0, 0.0, 0.0,
@@ -519,4 +523,4 @@ function addDefaults(gltf, stats) {
     textureDefaults(gltf);
 
     return gltf;
-};
+}