diff --git a/dom/locales/en-US/chrome/appstrings.properties b/dom/locales/en-US/chrome/appstrings.properties
index 27b0155aff82..dc98baacfde1 100644
--- a/dom/locales/en-US/chrome/appstrings.properties
+++ b/dom/locales/en-US/chrome/appstrings.properties
@@ -30,6 +30,7 @@ externalProtocolUnknown=<Unknown>
 externalProtocolChkMsg=Remember my choice for all links of this type.
 externalProtocolLaunchBtn=Launch application
 malwareBlocked=The site at %S has been reported as an attack site and has been blocked based on your security preferences.
+harmfulBlocked=The site at %S has been reported as a potentially harmful site and has been blocked based on your security preferences.
 unwantedBlocked=The site at %S has been reported as serving unwanted software and has been blocked based on your security preferences.
 deceptiveBlocked=This web page at %S has been reported as a deceptive site and has been blocked based on your security preferences.
 cspBlocked=This page has a content security policy that prevents it from being loaded in this way.