diff --git a/implementations/defs.txt b/implementations/defs.txt
index 6d0ed4d..185437c 100644
--- a/implementations/defs.txt
+++ b/implementations/defs.txt
@@ -136,3 +136,4 @@ _isnt_two_bools [_isnt_bool] ii
 _\/_ [_isnt_bool] [not] branch
 /\ _isnt_two_bools [pop false] [] branch
 \/ _isnt_two_bools [] [pop true] branch
+xor [] [not] branch