diff --git a/lib/chibi/binary-types.scm b/lib/chibi/binary-types.scm
index 908a7c96..69a55e41 100644
--- a/lib/chibi/binary-types.scm
+++ b/lib/chibi/binary-types.scm
@@ -91,7 +91,7 @@
      (define-syntax name
        (syntax-rules ()
          ((name . x)
-          (syntax-error "invalid use of auxilliary syntax" (name . x))))))))
+          (syntax-error "invalid use of auxiliary syntax" (name . x))))))))
 
 (define-auxiliary-syntax make:)
 (define-auxiliary-syntax pred:)