diff --git a/layout/style/test/mochitest.ini b/layout/style/test/mochitest.ini
index 2e47e98df6aa..9293545eea0d 100644
--- a/layout/style/test/mochitest.ini
+++ b/layout/style/test/mochitest.ini
@@ -190,7 +190,6 @@ skip-if = toolkit == 'android' #bug 536603
 [test_flexbox_flex_grow_and_shrink.html]
 [test_flexbox_flex_shorthand.html]
 [test_flexbox_focus_order.html]
-skip-if = toolkit == 'cocoa' # bug 1353992
 [test_flexbox_layout.html]
 support-files = flexbox_layout_testcases.js
 [test_flexbox_order.html]
diff --git a/layout/style/test/test_flexbox_focus_order.html b/layout/style/test/test_flexbox_focus_order.html
index 75bd7a9040eb..59aacd88d534 100644
--- a/layout/style/test/test_flexbox_focus_order.html
+++ b/layout/style/test/test_flexbox_focus_order.html
@@ -68,8 +68,14 @@ function doTest() {
   SimpleTest.finish();
 }
 
+// Before we start, we have to bump Mac to make its 'tab'-key focus behavior
+// predicatble:
+function begin() {
+  SpecialPowers.pushPrefEnv({ set: [[ "accessibility.tabfocus", 7 ]] }, doTest);
+}
+
 SimpleTest.waitForExplicitFinish();
-addLoadEvent(doTest);
+addLoadEvent(begin);
 
 </script>
 </pre>