diff --git a/layout/tools/reftest/output.py b/layout/tools/reftest/output.py
index 59c5f5523f73..f170634c6f67 100644
--- a/layout/tools/reftest/output.py
+++ b/layout/tools/reftest/output.py
@@ -128,6 +128,7 @@ class OutputHandler(object):
     def __init__(self, log, utilityPath, symbolsPath=None):
         self.stack_fixer_function = get_stack_fixer_function(utilityPath, symbolsPath)
         self.log = log
+        self.proc_name = None
 
     def __call__(self, line):
         # need to return processed messages to appease remoteautomation.py
@@ -151,4 +152,5 @@ class OutputHandler(object):
     def verbatim(self, line):
         if self.stack_fixer_function:
             line = self.stack_fixer_function(line)
-        self.log.process_output(threading.current_thread().name, line)
+        name = self.proc_name or threading.current_thread().name
+        self.log.process_output(name, line)
diff --git a/layout/tools/reftest/runreftest.py b/layout/tools/reftest/runreftest.py
index 105454605650..b7263da1004d 100644
--- a/layout/tools/reftest/runreftest.py
+++ b/layout/tools/reftest/runreftest.py
@@ -713,6 +713,7 @@ class RefTest(object):
                      interactive=interactive,
                      outputTimeout=timeout)
         proc = runner.process_handler
+        outputHandler.proc_name = 'GECKO({})'.format(proc.pid)
 
         # Used to defer a possible IOError exception from Marionette
         marionette_exception = None
@@ -749,6 +750,7 @@ class RefTest(object):
 
         status = runner.wait()
         runner.process_handler = None
+        outputHandler.proc_name = None
 
         if status:
             msg = "TEST-UNEXPECTED-FAIL | %s | application terminated with exit code %s" % \