--- a/layout/tools/reftest/runreftest.py
+++ b/layout/tools/reftest/runreftest.py
@@ -305,21 +305,22 @@ class RefTest(object):
             prefs['layers.acceleration.disabled'] = True
 
         sandbox_whitelist_paths = [SCRIPT_DIRECTORY]
         try:
             if options.workPath:
                 sandbox_whitelist_paths.append(options.workPath)
         except AttributeError:
             pass
-        try:
-            if options.objPath:
-                sandbox_whitelist_paths.append(options.objPath)
-        except AttributeError:
-            pass
+        if platform.system() == "Linux":
+            try:
+                if options.objPath:
+                    sandbox_whitelist_paths.append(options.objPath)
+            except AttributeError:
+                pass
         if (platform.system() == "Linux" or
             platform.system() in ("Windows", "Microsoft")):
             # Trailing slashes are needed to indicate directories on Linux and Windows
             sandbox_whitelist_paths = map(lambda p: os.path.join(p, ""),
                                           sandbox_whitelist_paths)
 
         # Bug 1300355: Disable canvas cache for win7 as it uses
         # too much memory and causes OOMs.