Index: /CKEditor/branches/prototype/_source/plugins/sourcearea/plugin.js
===================================================================
--- /CKEditor/branches/prototype/_source/plugins/sourcearea/plugin.js	(revision 2982)
+++ /CKEditor/branches/prototype/_source/plugins/sourcearea/plugin.js	(revision 2983)
@@ -96,9 +96,13 @@
 
 		editor.addCommand( 'source', sourcearea.commands.source );
-		editor.ui.addButton( 'Source',
-			{
-				label : editor.lang.source,
-				command : 'source'
-			});
+		
+		if ( editor.ui.addButton )
+		{
+			editor.ui.addButton( 'Source',
+				{
+					label : editor.lang.source,
+					command : 'source'
+				});
+		}
 
 		editor.on( 'mode', function()