diff --git a/UI/PreferencesUI/UIxJSONPreferences.m b/UI/PreferencesUI/UIxJSONPreferences.m
index 517c609cf..bd58cda91 100644
--- a/UI/PreferencesUI/UIxJSONPreferences.m
+++ b/UI/PreferencesUI/UIxJSONPreferences.m
@@ -337,7 +337,7 @@ static SoProduct *preferencesProduct = nil;
     [[defaults source] setObject: [defaults mailComposeMessageType] forKey: @"SOGoMailComposeMessageType"];
 
   if (![[defaults source] objectForKey: @"SOGoMailComposeFontSize"])
-    [[defaults source] setObject: [defaults mailComposeFontSize] forKey: @"SOGoMailComposeFontSize"];
+    [[defaults source] setInteger: [defaults mailComposeFontSize] forKey: @"SOGoMailComposeFontSize"];
 
   if (![[defaults source] objectForKey: @"SOGoMailDisplayRemoteInlineImages"])
     [[defaults source] setObject: [defaults mailDisplayRemoteInlineImages] forKey: @"SOGoMailDisplayRemoteInlineImages"];