diff --git a/application/basilisk/app/profile/basilisk.js b/application/basilisk/app/profile/basilisk.js
index f66436d3c9..1d8b0c6c26 100644
--- a/application/basilisk/app/profile/basilisk.js
+++ b/application/basilisk/app/profile/basilisk.js
@@ -923,7 +923,10 @@ pref("browser.tabs.remote.force-disable", false);
 pref("browser.tabs.remote.desktopbehavior", true);
 pref("browser.tabs.remote.ignoreBlockPolicy", true);
 // Number of web content processes used by e10s.
-pref("dom.ipc.processCount", 2);
+// -1 means automatic tab-isolation mode: try one process per tab.
+pref("dom.ipc.processCount", -1);
+// Safety ceiling used by automatic tab-isolation mode.
+pref("dom.ipc.processCount.webIsolatedMax", 64);
 
 // This pref governs whether we attempt to work around problems caused by
 // plugins using OS calls to manipulate the cursor while running out-of-