--- a/mozilla-tests/config.py
+++ b/mozilla-tests/config.py
@@ -79,17 +79,17 @@ PLATFORMS['macosx64']['slave_platforms']
 PLATFORMS['macosx64']['env_name'] = 'mac-perf'
 PLATFORMS['macosx64']['snowleopard'] = {'name': "Rev4 MacOSX Snow Leopard 10.6",
                                         'try_by_default': False}
 PLATFORMS['macosx64']['yosemite'] = {'name': "Rev5 MacOSX Yosemite 10.10",
                                      'try_by_default': False}
 PLATFORMS['macosx64']['yosemite_r7'] = {'name': "Rev7 MacOSX Yosemite 10.10.5"}
 PLATFORMS['macosx64']['stage_product'] = 'firefox'
 PLATFORMS['macosx64']['mozharness_config'] = {
-    'mozharness_python': '/tools/buildbot/bin/python',
+    'mozharness_python': ['/tools/buildbot/bin/python', '-u'],
     'hg_bin': 'hg',
     'reboot_command': ['/tools/buildbot/bin/python'] + MOZHARNESS_REBOOT_CMD,
     'config_file': 'talos/mac_config.py',
 }
 PLATFORMS['macosx64']['talos_slave_platforms'] = ['yosemite', 'yosemite_r7']
 
 PLATFORMS['win32']['slave_platforms'] = ['xp_ix', 'win7_ix', 'win7_vm', 'win7_vm_gfx']
 PLATFORMS['win32']['talos_slave_platforms'] = ['xp_ix', 'win7_ix']
@@ -123,17 +123,17 @@ PLATFORMS['win64']['mozharness_config'] 
     'config_file': 'talos/windows_config.py',
 }
 
 PLATFORMS['linux']['slave_platforms'] = ['ubuntu32_vm']
 PLATFORMS['linux']['env_name'] = 'linux-perf'
 PLATFORMS['linux']['ubuntu32_vm'] = {'name': 'Ubuntu VM 12.04'}
 PLATFORMS['linux']['stage_product'] = 'firefox'
 PLATFORMS['linux']['mozharness_config'] = {
-    'mozharness_python': '/tools/buildbot/bin/python',
+    'mozharness_python': ['/tools/buildbot/bin/python', '-u'],
     'hg_bin': 'hg',
     'reboot_command': ['/tools/buildbot/bin/python'] + MOZHARNESS_REBOOT_CMD,
     'config_file': 'talos/linux_config.py',
 }
 
 
 PLATFORMS['linux64']['slave_platforms'] = ['ubuntu64_vm', 'ubuntu64_vm_lnx_large']
 PLATFORMS['linux64']['talos_slave_platforms'] = ['ubuntu64_hw']