diff --git a/examples/index.css b/examples/index.css
index c9d82a275..c72284241 100644
--- a/examples/index.css
+++ b/examples/index.css
@@ -16,6 +16,7 @@ p {
 pre {
   padding: 10px;
   background-color: #eee;
+  white-space: pre-wrap;
 }
 
 img {
diff --git a/lib/models/node.js b/lib/models/node.js
index 80f49260b..c50e43904 100644
--- a/lib/models/node.js
+++ b/lib/models/node.js
@@ -857,7 +857,10 @@ const Node = {
       let ret = node
       if (ret.kind != 'text') ret = ret.mapDescendants(iterator)
       ret = iterator(ret, i, this.nodes)
-      if (ret != node) nodes = nodes.set(ret.key, ret)
+      if (ret == node) return
+
+      const index = nodes.indexOf(node)
+      nodes = nodes.set(index, ret)
     })
 
     return this.merge({ nodes })
diff --git a/test/rendering/fixtures/custom-decorator/index.js b/test/rendering/fixtures/custom-decorator/index.js
new file mode 100644
index 000000000..9c64b3cc8
--- /dev/null
+++ b/test/rendering/fixtures/custom-decorator/index.js
@@ -0,0 +1,21 @@
+
+import React from 'react'
+import { Mark } from '../../../..'
+
+const BOLD = {
+  fontWeight: 'bold'
+}
+
+export function renderMark(mark) {
+  if (mark.type == 'bold') return BOLD
+}
+
+export function renderDecorations(text) {
+  let { characters } = text
+  let second = characters.get(1)
+  let mark = Mark.create({ type: 'bold' })
+  let marks = second.marks.add(mark)
+  second = second.merge({ marks })
+  characters = characters.set(1, second)
+  return characters
+}
diff --git a/test/rendering/fixtures/custom-decorator/input.yaml b/test/rendering/fixtures/custom-decorator/input.yaml
new file mode 100644
index 000000000..9b822c1a1
--- /dev/null
+++ b/test/rendering/fixtures/custom-decorator/input.yaml
@@ -0,0 +1,8 @@
+
+nodes:
+  - kind: block
+    type: default
+    nodes:
+      - kind: text
+        ranges:
+          - text: one
diff --git a/test/rendering/fixtures/custom-decorator/output.html b/test/rendering/fixtures/custom-decorator/output.html
new file mode 100644
index 000000000..1e8974b3a
--- /dev/null
+++ b/test/rendering/fixtures/custom-decorator/output.html
@@ -0,0 +1,10 @@
+
+<div contenteditable="true">
+  <div>
+    <span>
+      <span>o</span>
+      <span style="font-weight:bold;">n</span>
+      <span>e</span>
+    </span>
+  </div>
+</div>