--- a/testing/xpcshell/mach_commands.py
+++ b/testing/xpcshell/mach_commands.py
@@ -65,17 +65,17 @@ class XPCShellRunner(MozbuildObject):
         build_path = os.path.join(self.topobjdir, 'build')
         if build_path not in sys.path:
             sys.path.append(build_path)
 
         src_build_path = os.path.join(self.topsrcdir, 'mozilla', 'build')
         if os.path.isdir(src_build_path):
             sys.path.append(src_build_path)
 
-        self.run_suite(**kwargs)
+        return self.run_suite(**kwargs)
 
 
     def _run_xpcshell_harness(self, **kwargs):
         # Obtain a reference to the xpcshell test runner.
         import runxpcshelltests
 
         log = kwargs.pop("log")