--- a/python/mozbuild/mozbuild/mach_commands.py
+++ b/python/mozbuild/mozbuild/mach_commands.py
@@ -1055,16 +1055,18 @@ class RunProgram(MachCommandBase):
         help='Command-line arguments to be passed through to the program. Not specifying a --profile or -P option will result in a temporary profile being used.')
     @CommandArgumentGroup(prog_group)
     @CommandArgument('--remote', '-r', action='store_true', group=prog_group,
         help='Do not pass the --no-remote argument by default.')
     @CommandArgument('--background', '-b', action='store_true', group=prog_group,
         help='Do not pass the --foreground argument by default on Mac.')
     @CommandArgument('--noprofile', '-n', action='store_true', group=prog_group,
         help='Do not pass the --profile argument by default.')
+    @CommandArgument('--disable-e10s', action='store_true', group=prog_group,
+        help='Run the program with electrolysis disabled.')
 
     @CommandArgumentGroup('debugging')
     @CommandArgument('--debug', action='store_true', group='debugging',
         help='Enable the debugger. Not specifying a --debugger option will result in the default debugger being used.')
     @CommandArgument('--debugger', default=None, type=str, group='debugging',
         help='Name of debugger to use.')
     @CommandArgument('--debugparams', default=None, metavar='params', type=str,
         group='debugging',
@@ -1081,18 +1083,18 @@ class RunProgram(MachCommandBase):
     @CommandArgument('--dmd', action='store_true', group='DMD',
         help='Enable DMD. The following arguments have no effect without this.')
     @CommandArgument('--mode', choices=['live', 'dark-matter', 'cumulative', 'scan'], group='DMD',
          help='Profiling mode. The default is \'dark-matter\'.')
     @CommandArgument('--stacks', choices=['partial', 'full'], group='DMD',
         help='Allocation stack trace coverage. The default is \'partial\'.')
     @CommandArgument('--show-dump-stats', action='store_true', group='DMD',
         help='Show stats when doing dumps.')
-    def run(self, params, remote, background, noprofile, debug, debugger,
-        debugparams, slowscript, dmd, mode, stacks, show_dump_stats):
+    def run(self, params, remote, background, noprofile, disable_e10s, debug,
+        debugger, debugparams, slowscript, dmd, mode, stacks, show_dump_stats):
 
         if conditions.is_android(self):
             # Running Firefox for Android is completely different
             if dmd:
                 print("DMD is not supported for Firefox for Android")
                 return 1
             from mozrunner.devices.android_device import verify_android_device, run_firefox_for_android
             if not (debug or debugger or debugparams):
@@ -1127,16 +1129,18 @@ class RunProgram(MachCommandBase):
             if no_profile_option_given and not noprofile:
                 path = os.path.join(self.topobjdir, 'tmp', 'scratch_user')
                 if not os.path.isdir(path):
                     os.makedirs(path)
                 args.append('-profile')
                 args.append(path)
 
         extra_env = {'MOZ_CRASHREPORTER_DISABLE': '1'}
+        if disable_e10s:
+            extra_env['MOZ_FORCE_DISABLE_E10S'] = '1'
 
         if debug or debugger or debugparams:
             if 'INSIDE_EMACS' in os.environ:
                 self.log_manager.terminal_handler.setLevel(logging.WARNING)
 
             import mozdebug
             if not debugger:
                 # No debugger name was provided. Look for the default ones on

--- a/toolkit/xre/nsAppRunner.cpp
+++ b/toolkit/xre/nsAppRunner.cpp
@@ -4711,17 +4711,18 @@ mozilla::BrowserTabsRemoteAutostart()
   if (Preferences::GetBool(kForceEnableE10sPref, false)) {
     gBrowserTabsRemoteAutostart = true;
     prefEnabled = true;
     status = kE10sEnabledByUser;
   }
 
   // Uber override pref for emergency blocking
   if (gBrowserTabsRemoteAutostart &&
-      Preferences::GetBool(kForceDisableE10sPref, false)) {
+      (Preferences::GetBool(kForceDisableE10sPref, false) ||
+       EnvHasValue("MOZ_FORCE_DISABLE_E10S"))) {
     gBrowserTabsRemoteAutostart = false;
     status = kE10sForceDisabled;
   }
 
   gBrowserTabsRemoteStatus = status;
 
   mozilla::Telemetry::Accumulate(mozilla::Telemetry::E10S_STATUS, status);
   if (prefEnabled) {