Index: /CKEditor/trunk/CHANGES.html
===================================================================
--- /CKEditor/trunk/CHANGES.html	(revision 3951)
+++ /CKEditor/trunk/CHANGES.html	(revision 3952)
@@ -165,4 +165,5 @@
 		<li><a href="http://dev.fckeditor.net/ticket/3988">#3988</a> : Destroy editor on form submit event cause error.</li>
 		<li><a href="http://dev.fckeditor.net/ticket/3994">#3994</a> : Insert horizontal line at end of document cause error.</li>
+		<li><a href="http://dev.fckeditor.net/ticket/4074">#4074</a> : Indent error with 'indentClasses' config specified.</li>
 		<li><a href="http://dev.fckeditor.net/ticket/4057">#4057</a> : Fixed anchor is lost after switch between editing modes.</li>
 	</ul>
Index: /CKEditor/trunk/_source/plugins/indent/plugin.js
===================================================================
--- /CKEditor/trunk/_source/plugins/indent/plugin.js	(revision 3951)
+++ /CKEditor/trunk/_source/plugins/indent/plugin.js	(revision 3952)
@@ -70,5 +70,5 @@
 			}
 			if ( ( this.name == 'outdent' && !indentStep ) ||
-					( this.name == 'indent' && indentStep == editor.config.indentClass.length ) )
+					( this.name == 'indent' && indentStep == editor.config.indentClasses.length ) )
 				return setState.call( this, editor, CKEDITOR.TRISTATE_DISABLED );
 			return setState.call( this, editor, CKEDITOR.TRISTATE_OFF );