diff --git a/toolkit/forgetaboutsite/ForgetAboutSite.jsm b/toolkit/forgetaboutsite/ForgetAboutSite.jsm
index b8cd31ad9c..5250ca75d4 100644
--- a/toolkit/forgetaboutsite/ForgetAboutSite.jsm
+++ b/toolkit/forgetaboutsite/ForgetAboutSite.jsm
@@ -126,7 +126,7 @@ this.ForgetAboutSite = {
     // XXXehsan: is there a better way to do this rather than this
     // hacky comparison?
     catch (ex) {
-      if (ex.message.indexOf("User canceled Master Password entry") == -1) {
+      if (!ex.message.includes("User canceled Master Password entry")) {
         throw ex;
       }
     }