diff --git a/src/js/models/post-node-builder.js b/src/js/models/post-node-builder.js
index 6568548e9..c53fb0b88 100644
--- a/src/js/models/post-node-builder.js
+++ b/src/js/models/post-node-builder.js
@@ -65,19 +65,21 @@ export default class PostNodeBuilder {
     return marker;
   }
 
-  createMarkup(tagName, attributes) {
+  // Attributes is an array of [key1, value1, key2, value2, ...]
+  createMarkup(tagName, attributes=[]) {
     tagName = normalizeTagName(tagName);
 
     let markup;
 
-    if (attributes) {
+    if (attributes.length) {
       // FIXME: This could also be cached
       markup = new Markup(tagName, attributes);
     } else {
-      if (this.markupCache[tagName]) {
-        markup = this.markupCache[tagName];
-      } else {
+      markup = this.markupCache[tagName];
+
+      if (!markup) {
         markup = new Markup(tagName, attributes);
+        this.markupCache[tagName] = markup;
       }
     }
 
diff --git a/tests/acceptance/editor-commands-test.js b/tests/acceptance/editor-commands-test.js
index 44a6f48e9..2c8b8fe72 100644
--- a/tests/acceptance/editor-commands-test.js
+++ b/tests/acceptance/editor-commands-test.js
@@ -60,6 +60,32 @@ test('highlight text, click "bold" button bolds text', (assert) => {
   });
 });
 
+test('highlight text, click "bold", type more text, re-select text, bold button is active', (assert) => {
+  let done = assert.async();
+
+  setTimeout(() => {
+    Helpers.toolbar.clickButton(assert, 'bold');
+    assert.hasElement('#editor strong:contains(IS A)');
+
+    let boldTag = $('#editor strong:contains(IS A)')[0];
+    let textNode = boldTag.childNodes[0];
+    assert.equal(textNode.textContent, 'IS A', 'precond - correct node');
+
+    Helpers.dom.moveCursorTo(textNode, 'IS'.length);
+    Helpers.dom.insertText('X');
+
+    assert.hasElement('strong:contains(ISX A)', 'adds text to bold');
+
+    Helpers.dom.selectText('ISX A', editorElement);
+    Helpers.dom.triggerEvent(document, 'mouseup');
+
+    setTimeout(() => {
+      Helpers.toolbar.assertActiveButton(assert, 'bold');
+      done();
+    });
+  });
+});
+
 test('highlight text, click "heading" button turns text into h2 header', (assert) => {
   const done = assert.async();
 
diff --git a/tests/unit/models/markup-section-test.js b/tests/unit/models/markup-section-test.js
index 1ec621fae..eb1b56c2a 100644
--- a/tests/unit/models/markup-section-test.js
+++ b/tests/unit/models/markup-section-test.js
@@ -20,6 +20,20 @@ test('a section can append a marker', (assert) => {
   assert.equal(s1.markers.length, 1);
 });
 
+test('postNodeBuilder#createMarkup returns a singleton object when it has no attributes', (assert) => {
+  let markup = builder.createMarkup('b');
+
+  let others = [
+    builder.createMarkup('B'),
+    builder.createMarkup('B', []),
+    builder.createMarkup('b', [])
+  ];
+
+  others.forEach(other => {
+    assert.ok(markup === other, 'markup is the same object');
+  });
+});
+
 test('#splitMarker splits the marker at the offset', (assert) => {
   const m1 = builder.createMarker('hi ');
   const m2 = builder.createMarker('there!');