diff --git a/toolkit/locales/en-US/chrome/mozapps/extensions/extensions.properties b/toolkit/locales/en-US/chrome/mozapps/extensions/extensions.properties
index cfbc12633ee4..13e980a740f3 100644
--- a/toolkit/locales/en-US/chrome/mozapps/extensions/extensions.properties
+++ b/toolkit/locales/en-US/chrome/mozapps/extensions/extensions.properties
@@ -16,6 +16,8 @@ droppedInWarning=The following items were found in your Extensions folder. Do yo
 updateNotificationTitle=Add-on updates found
 updateNotificationText=%S has found an update for 1 of your add-ons
 multipleUpdateNotificationText=%S has found updates for %S of your add-ons
+# LOCALIZATION NOTE (lightweightThemeDescription): %S is the theme designer, either a person or organisation
+lightweightThemeDescription=Created by %S.
 
 uninstallButton=Uninstall
 disableButton=Disable