diff --git a/UI/MailerUI/UIxMailMainFrame.m b/UI/MailerUI/UIxMailMainFrame.m
index bc5d6930f..99ce6edc7 100644
--- a/UI/MailerUI/UIxMailMainFrame.m
+++ b/UI/MailerUI/UIxMailMainFrame.m
@@ -328,12 +328,17 @@
 
 - (WOResponse *) getFoldersStateAction
 {
-  NSString *expandedFolders;
+  id o;
+  NSArray *expandedFolders;
 
   [self _setupContext];
-  expandedFolders = [moduleSettings objectForKey: @"ExpandedFolders"];
+  o = [moduleSettings objectForKey: @"ExpandedFolders"];
+  if ([o isKindOfClass: [NSString class]])
+    expandedFolders = [o componentsSeparatedByString: @","];
+  else
+    expandedFolders = o;
 
-  return [self responseWithStatus: 200 andString: expandedFolders];
+  return [self responseWithStatus: 200 andJSONRepresentation: expandedFolders];
 }
 
 - (NSString *) verticalDragHandleStyle