diff --git a/grudge/symbolic/primitives.py b/grudge/symbolic/primitives.py
index 0a49034568f6ec45c25b45018e9451fb866fe361..1daf063a401db2ef13aed97c25901f48431e3f57 100644
--- a/grudge/symbolic/primitives.py
+++ b/grudge/symbolic/primitives.py
@@ -701,8 +701,8 @@ class TracePair:
     def __getitem__(self, index):
         return TracePair(
                 self.dd,
-                self.exterior[index],
-                self.interior[index])
+                interior=self.interior[index],
+                exterior=self.exterior[index])
 
     def __len__(self):
         assert len(self.exterior) == len(self.interior)