diff --git a/extensions/firefox/install.rdf.in b/extensions/firefox/install.rdf.in
index 3f8f87cda..feab3e7ad 100644
--- a/extensions/firefox/install.rdf.in
+++ b/extensions/firefox/install.rdf.in
@@ -20,7 +20,7 @@
true
Mozilla
Uses HTML5 to display PDF files directly in Firefox.
- http://support.mozilla.org/kb/using-mozilla-pdf-viewer
+ https://support.mozilla.org/kb/Opening%20PDF%20files%20within%20Firefox
2