--- a/dom/ipc/ContentPrefs.cpp
+++ b/dom/ipc/ContentPrefs.cpp
@@ -182,16 +182,17 @@ const char* mozilla::dom::ContentPrefs::
   "layout.css.stylo-blocklist.enabled",
 #endif
   "layout.css.text-align-unsafe-value.enabled",
   "layout.css.text-combine-upright-digits.enabled",
   "layout.css.text-combine-upright.enabled",
   "layout.css.text-justify.enabled",
   "layout.css.touch_action.enabled",
   "layout.css.visited_links_enabled",
+  "layout.css.webkit-appearance.enabled",
   "layout.idle_period.required_quiescent_frames",
   "layout.idle_period.time_limit",
   "layout.interruptible-reflow.enabled",
   "mathml.disabled",
   "media.audio-max-decode-error",
   "media.cache_readahead_limit",
   "media.cache_resume_threshold",
   "media.cache_size",