diff --git a/formats/indent.js b/formats/indent.js
index 43a92ece0c..a0c05ef2cd 100644
--- a/formats/indent.js
+++ b/formats/indent.js
@@ -14,8 +14,8 @@ class IdentAttributor extends Parchment.Attributor.Class {
     }
   }
 
-  value(node){
-    return parseInt(super.value(node));
+  value(node) {
+    return parseInt(super.value(node)) || undefined;  // Don't return NaN
   }
 }
 
diff --git a/test/unit.js b/test/unit.js
index e0d3787c49..38d0be08dd 100644
--- a/test/unit.js
+++ b/test/unit.js
@@ -16,6 +16,7 @@ import './unit/formats/script';
 import './unit/formats/align';
 import './unit/formats/code';
 import './unit/formats/header';
+import './unit/formats/indent';
 import './unit/formats/list';
 
 import './unit/modules/clipboard';
diff --git a/test/unit/formats/indent.js b/test/unit/formats/indent.js
new file mode 100644
index 0000000000..1f00c53c6b
--- /dev/null
+++ b/test/unit/formats/indent.js
@@ -0,0 +1,19 @@
+import Delta from 'rich-text/lib/delta';
+import Editor from '../../../core/editor';
+
+
+describe('Indent', function() {
+  it('+1', function() {
+    let editor = this.initialize(Editor, '<ul><li>0123</li></ul>');
+    editor.formatText(4, 1, { 'indent': '+1' });
+    expect(editor.getDelta()).toEqual(new Delta().insert('0123').insert('\n', { list: 'bullet', indent: 1 }));
+    expect(editor.scroll.domNode).toEqualHTML('<ul><li class="ql-indent-1">0123</li></ul>');
+  });
+
+  it('-1', function() {
+    let editor = this.initialize(Editor, '<ul><li class="ql-indent-1">0123</li></ul>');
+    editor.formatText(4, 1, { 'indent': '-1' });
+    expect(editor.getDelta()).toEqual(new Delta().insert('0123').insert('\n', { list: 'bullet' }));
+    expect(editor.scroll.domNode).toEqualHTML('<ul><li>0123</li></ul>');
+  });
+});