diff --git a/toolkit/components/reader/ReaderMode.jsm b/toolkit/components/reader/ReaderMode.jsm
index 5ba898aec..d9889e19e 100644
--- a/toolkit/components/reader/ReaderMode.jsm
+++ b/toolkit/components/reader/ReaderMode.jsm
@@ -14,7 +14,7 @@ const CLASSES_TO_PRESERVE = [
   "caption",
   "emoji",
   "hidden",
-  "invisble",
+  "invisible",
   "sr-only",
   "visually-hidden",
   "visuallyhidden",