diff --git a/mozilla/modules/libpref/src/init/all.js b/mozilla/modules/libpref/src/init/all.js
index 6195cc24673..62d2e1bb116 100644
--- a/mozilla/modules/libpref/src/init/all.js
+++ b/mozilla/modules/libpref/src/init/all.js
@@ -1163,7 +1163,6 @@ pref("font.name.monospace.zh-HK", "Apple LiGothic Medium");
 pref("font.name.cursive.zh-HK", "XXX.cursive");
 pref("font.name.fantasy.zh-HK", "XXX.fantasy");
 
-pref("font.default", "serif");
 pref("font.default", "serif");
 pref("font.size.variable.ar", 15);
 pref("font.size.fixed.ar", 13);