diff --git a/web/firefox/mozconfig b/web/firefox/mozconfig
index a95a84757fb..8625e566aa9 100644
--- a/web/firefox/mozconfig
+++ b/web/firefox/mozconfig
@@ -30,5 +30,8 @@ ac_add_options --disable-necko-wifi
 ac_add_options --disable-gnomevfs
 ac_add_options --enable-system-cairo
 
-#Disabling tests breaks PGO so having CONFIGURE set it 
+# startupcache deterministically segfaults on *some* systems. Just leave it disabled.
+ac_add_options --disable-startupcache
+
+# Disabling tests breaks PGO so having CONFIGURE set it
 #ac_add_options --disable-tests