diff --git a/layout/tools/reftest/mach_commands.py b/layout/tools/reftest/mach_commands.py
index 428e44a9299..9807633c808 100644
--- a/layout/tools/reftest/mach_commands.py
+++ b/layout/tools/reftest/mach_commands.py
@@ -364,7 +364,7 @@ class MachCommands(MachCommandBase):
 # they should be modified to work with all devices.
 def is_emulator(cls):
     """Emulator needs to be configured."""
-    return cls.device_name in ('emulator', 'emulator-jb')
+    return cls.device_name.find('emulator') == 0
 
 
 @CommandProvider
diff --git a/testing/marionette/mach_commands.py b/testing/marionette/mach_commands.py
index 468e5933b81..e49e73ca4b4 100644
--- a/testing/marionette/mach_commands.py
+++ b/testing/marionette/mach_commands.py
@@ -77,7 +77,7 @@ class B2GCommands(MachCommandBase):
     @CommandArgument('tests', nargs='*', metavar='TESTS',
         help='Path to test(s) to run.')
     def run_marionette_webapi(self, tests, emulator=None, testtype=None):
-        if not emulator and self.device_name in ('emulator', 'emulator-jb'):
+        if not emulator and self.device_name.find('emulator') == 0:
             emulator='arm'
 
         if self.substs.get('ENABLE_MARIONETTE') != '1':
diff --git a/testing/mochitest/mach_commands.py b/testing/mochitest/mach_commands.py
index 2efadc76b92..dc1080d74a7 100644
--- a/testing/mochitest/mach_commands.py
+++ b/testing/mochitest/mach_commands.py
@@ -637,7 +637,7 @@ class MachCommands(MachCommandBase):
 # they should be modified to work with all devices.
 def is_emulator(cls):
     """Emulator needs to be configured."""
-    return cls.device_name in ('emulator', 'emulator-jb')
+    return cls.device_name.find('emulator') == 0
 
 
 @CommandProvider