diff --git a/font-face.rkt b/font-face.rkt
index e1d646b..5ec05fc 100644
--- a/font-face.rkt
+++ b/font-face.rkt
@@ -6,6 +6,7 @@
 
 (module+ test (require rackunit))
 
+(require racket/contract sugar)
 
 (define/contract (base64-font-string? x)
   (any/c . -> . boolean?)
diff --git a/gradient.rkt b/gradient.rkt
index 1274b33..e69de29 100644
--- a/gradient.rkt
+++ b/gradient.rkt
@@ -1,5 +0,0 @@
-#lang racket/base
-(require "core.rkt" racket/list racket/string)
-
-(provide (all-defined-out))
-
diff --git a/transition.rkt b/transition.rkt
index fff07c8..14cf7f5 100644
--- a/transition.rkt
+++ b/transition.rkt
@@ -10,7 +10,7 @@
                       (make-css-strings transition-prefixes "transition-duration" duration)
                       (if timing-function
                           (make-css-strings transition-prefixes "transition-timing-function" timing-function)
-                          empty)
+                          '())
                       (if delay
                           (make-css-strings transition-prefixes "transition-delay" delay)
-                          empty))))
+                          '()))))