diff --git a/js/view/ISLCPullerNode.js b/js/view/ISLCPullerNode.js
index 7a9f07e..d5b1743 100644
--- a/js/view/ISLCPullerNode.js
+++ b/js/view/ISLCPullerNode.js
@@ -64,7 +64,7 @@ define( function( require ) {
 
     // if in coulomb's law, add pusher and zero force images in proper order
     if ( options.attractNegative ) {
-      var zeroForceIndex = pushImages.length;
+      zeroForceIndex = pushImages.length;
       this.pullerPusherImages = pushImages.concat( zeroForceImage ).concat( pullImages );
     }