--- a/testing/xpcshell/mach_commands.py
+++ b/testing/xpcshell/mach_commands.py
@@ -137,19 +137,20 @@ class XPCShellRunner(MozbuildObject):
 
         xpcshell_filter = TestStartFilter()
         self.log_manager.terminal_handler.addFilter(xpcshell_filter)
 
         tests_dir = os.path.join(self.topobjdir, '_tests', 'xpcshell')
         modules_dir = os.path.join(self.topobjdir, '_tests', 'modules')
         # We want output from the test to be written immediately if we are only
         # running a single test.
-        verbose_output = (test_path is not None or
-                          (manifest and len(manifest.test_paths())==1) or
-                          verbose)
+        single_test = (test_path is not None or
+                       (manifest and len(manifest.test_paths())==1))
+        verbose_output = verbose or single_test
+        sequential = sequential or single_test
 
         args = {
             'manifest': manifest,
             'xpcshell': self.get_binary_path('xpcshell'),
             'mozInfo': os.path.join(self.topobjdir, 'mozinfo.json'),
             'symbolsPath': os.path.join(self.distdir, 'crashreporter-symbols'),
             'interactive': interactive,
             'keepGoing': keep_going,