--- a/dom/locales/en-US/chrome/security/security.properties
+++ b/dom/locales/en-US/chrome/security/security.properties
@@ -89,10 +89,12 @@ BlockScriptWithWrongMimeType=Script from “%1$S” was blocked because of a disallowed MIME type.
 BlockTopLevelDataURINavigation=Navigation to toplevel data: URI not allowed (Blocked loading of: “%1$S”)
 BlockSubresourceRedirectToData=Redirecting to insecure data: URI not allowed (Blocked loading of: “%1$S”)
 
 BlockSubresourceFTP=Loading FTP subresource within http(s) page not allowed (Blocked loading of: “%1$S”)
 
 # LOCALIZATION NOTE (BrowserUpgradeInsecureDisplayRequest):
 # %1$S is the browser name "brandShortName"; %2$S is the URL of the upgraded request; %1$S is the upgraded scheme.
 BrowserUpgradeInsecureDisplayRequest = %1$S is upgrading an insecure display request ‘%2$S’ to use ‘%3$S’
-RunningClearSiteDataValue=Clear-Site-Data header forces the clean up of “%S” data.
+# LOCALIZATION NOTE (RunningClearSiteDataValue):
+# %S is the URI of the resource whose data was cleaned up
+RunningClearSiteDataValue=Clear-Site-Data header forced the clean up of “%S” data.
 UnknownClearSiteDataValue=Clear-Site-Data header found. Unknown value “%S”.