diff --git a/d3.layout.js b/d3.layout.js
index a130b615..56b28c7d 100644
--- a/d3.layout.js
+++ b/d3.layout.js
@@ -560,12 +560,18 @@ function d3_layout_forceAccumulate(quad) {
       cy = 0;
   quad.count = 0;
   if (!quad.leaf) {
-    quad.nodes.forEach(function(c) {
+    var nodes = quad.nodes,
+        n = nodes.length,
+        i = -1,
+        c;
+    while (++i < n) {
+      c = nodes[i];
+      if (c == null) continue;
       d3_layout_forceAccumulate(c);
       quad.count += c.count;
       cx += c.count * c.cx;
       cy += c.count * c.cy;
-    });
+    }
   }
   if (quad.point) {
     // jitter internal nodes that are coincident
diff --git a/d3.layout.min.js b/d3.layout.min.js
index c6b3c2c6..c6d55ea6 100644
--- a/d3.layout.min.js
+++ b/d3.layout.min.js
@@ -1 +1 @@
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diff --git a/src/layout/force.js b/src/layout/force.js
index 771af878..8b4d5913 100644
--- a/src/layout/force.js
+++ b/src/layout/force.js
@@ -354,12 +354,18 @@ function d3_layout_forceAccumulate(quad) {
       cy = 0;
   quad.count = 0;
   if (!quad.leaf) {
-    quad.nodes.forEach(function(c) {
+    var nodes = quad.nodes,
+        n = nodes.length,
+        i = -1,
+        c;
+    while (++i < n) {
+      c = nodes[i];
+      if (c == null) continue;
       d3_layout_forceAccumulate(c);
       quad.count += c.count;
       cx += c.count * c.cx;
       cy += c.count * c.cy;
-    });
+    }
   }
   if (quad.point) {
     // jitter internal nodes that are coincident