diff --git a/guix/http-client.scm b/guix/http-client.scm
index 8d1cc9b8f33101b038ae53600997028d8934db4f..bee8cdc83425ef3fbcce574bf8c41d7ea40274d3 100644
--- a/guix/http-client.scm
+++ b/guix/http-client.scm
@@ -241,7 +241,7 @@ (define* (http-fetch uri #:key port (text? #f) (buffered? #t))
 ;;; Caching.
 ;;;
 
-(define (%http-cache-ttl)
+(define %http-cache-ttl
   ;; Time-to-live in seconds of the HTTP cache of in ~/.cache/guix.
   (make-parameter
    (* 3600 (or (and=> (getenv "GUIX_HTTP_CACHE_TTL")