diff --git a/lib/ansible/plugins/filter/mathstuff.py b/lib/ansible/plugins/filter/mathstuff.py
index 390727b8c6f..403f7523822 100644
--- a/lib/ansible/plugins/filter/mathstuff.py
+++ b/lib/ansible/plugins/filter/mathstuff.py
@@ -65,7 +65,8 @@ def symmetric_difference(a, b):
     if isinstance(a, collections.Hashable) and isinstance(b, collections.Hashable):
         c = set(a) ^ set(b)
     else:
-        c = unique([x for x in union(a, b) if x not in intersect(a, b)])
+        isect = intersect(a, b)
+        c = [x for x in union(a, b) if x not in isect]
     return c