diff --git a/layout/tools/reftest/runreftest.py b/layout/tools/reftest/runreftest.py
index 3a45e760d7f9..2ac544a0c6ea 100644
--- a/layout/tools/reftest/runreftest.py
+++ b/layout/tools/reftest/runreftest.py
@@ -625,7 +625,7 @@ class ReftestOptions(OptionParser):
     # Certain paths do not make sense when we're cross compiling Fennec.  This
     # logic is cribbed from the example in
     # python/mozbuild/mozbuild/mach_commands.py.
-    defaults['appname'] = build_obj.get_binary_path() if \
+    defaults['app'] = build_obj.get_binary_path() if \
         build_obj and build_obj.substs['MOZ_BUILD_APP'] != 'mobile/android' else None
 
     self.add_option("--extra-profile-file",