diff --git a/lib/loadObj.js b/lib/loadObj.js
index e38465c..293fdc6 100644
--- a/lib/loadObj.js
+++ b/lib/loadObj.js
@@ -330,7 +330,7 @@ function loadObj(objPath, options) {
 
     // Given the cartesian 2 vertices of a polygon, determine if convex
     function isConvex(positions2D) {
-        var length = position2D.length;
+        var length = positions2D.length;
         var turnDirection = getTurnDirection(positions2D[0], positions2D[1], positions2D[2]);
         for (var i=1; i < length-2; ++i) {
             var currentTurnDirection = getTurnDirection(positions2D[i], positions2D[i+1], positions2D[i+2]);
@@ -338,11 +338,11 @@ function loadObj(objPath, options) {
                 return false;
             }
         }
-        var currentTurnDirection = getTurnDirection(position2D[length-2], position2D[length-1], position2D[0]);
+        var currentTurnDirection = getTurnDirection(positions2D[length-2], positions2D[length-1], positions2D[0]);
         if (turnDirection * currentTurnDirection < 0) {
 	        return false;
         }
-        currentTurnDirection = getTurnDirection(position2D[length-1], position2D[0], position2D[1]);
+        currentTurnDirection = getTurnDirection(positions2D[length-1], positions2D[0], positions2D[1]);
         if (turnDirection * currentTurnDirection < 0) {
 	        return false;
         }