diff --git a/mapper/mapper.go b/mapper/mapper.go
index 4869c7b..ce172de 100644
--- a/mapper/mapper.go
+++ b/mapper/mapper.go
@@ -100,6 +100,8 @@
 	LayerA      string
 	FoundryB    string
 	LayerB      string
+	FieldA      string
+	FieldB      string
 	Direction   Direction
 	AddRewrites bool
 }