diff --git a/docs/routing/bird/bird.md b/docs/routing/bird/bird.md
index 6cd180c..d331796 100644
--- a/docs/routing/bird/bird.md
+++ b/docs/routing/bird/bird.md
@@ -88,7 +88,7 @@ filter crxnFilter
 }
 ```
 
-TODO: Add a check about not installing RTD_UNREACHABLEs which babel will generate sometimes and which BIRD reportedly has undefined behaviour with
+TODO: Add a check about not installing RTD_UNREACHABLEs which babel will generate sometimes and which BIRD reportedly has undefined behavior with
 
 ---