--- a/toolkit/xre/nsAppRunner.cpp
+++ b/toolkit/xre/nsAppRunner.cpp
@@ -5162,20 +5162,26 @@ GetMaxWebProcessCount()
 
   // If the user has set dom.ipc.processCount, respect their decision
   // regardless of add-ons that might affect their experience or experiment
   // cohort.
   if (Preferences::HasUserValue(optInPref)) {
     return std::max(1u, optInPrefValue);
   }
 
+#ifdef RELEASE_OR_BETA
+  // For our rollout on Release and Beta, we set this pref from the
+  // e10srollout extension. On Nightly, we don't touch the pref at all,
+  // allowing stale values to disable e10s-multi for certain users.
   if (Preferences::HasUserValue("dom.ipc.processCount.web")) {
     // The user didn't opt in or out so read the .web version of the pref.
     return std::max(1, Preferences::GetInt("dom.ipc.processCount.web", 1));
   }
+#endif
+
   return optInPrefValue;
 }
 
 const char*
 PlatformBuildID()
 {
   return gToolkitBuildID;
 }