diff --git a/caravel/assets/visualizations/treemap.js b/caravel/assets/visualizations/treemap.js
index 88ed230060a85..d37108526af2b 100644
--- a/caravel/assets/visualizations/treemap.js
+++ b/caravel/assets/visualizations/treemap.js
@@ -72,11 +72,16 @@ function treemap(slice) {
     // We also take a snapshot of the original children (_children) to avoid
     // the children being overwritten when when layout is computed.
     var accumulate = function (d) {
-      return (d._children = d.children)
-          ? d.value = d.children.reduce(function (p, v) { return p + accumulate(v); }, 0)
-          : d.value;
+      var results;
+      if (d._children === d.children) {
+        results = d.children.reduce(function (p, v) { return p + accumulate(v); }, 0);
+      } else {
+        results = d.value;
+      }
+      return results;
     };
 
+
     // Compute the treemap layout recursively such that each group of siblings
     // uses the same size (1x1) rather than the dimensions of the parent cell.
     // This optimizes the layout for the current zoom state. Note that a wrapper