diff --git a/functions.rkt b/functions.rkt
index 375ecfe..a39e09d 100644
--- a/functions.rkt
+++ b/functions.rkt
@@ -253,8 +253,7 @@
 ;;; Applying a TBF consists in multiplying the weights by the
 ;;; corresponding inputs and comparing the sum of the products to the
 ;;; threshold.
-(define/contract (apply-tbf tbf inputs)
-  (-> tbf? (vectorof (or/c 0 1)) (or/c 0 1))
+(define (apply-tbf tbf inputs)
   (any->01
    (>
     ;; The scalar product between the inputs and the weights