diff --git a/lib/tree-updater.rkt b/lib/tree-updater.rkt
index 074c5a1..bf9f82c 100644
--- a/lib/tree-updater.rkt
+++ b/lib/tree-updater.rkt
@@ -100,6 +100,9 @@
   (define (cardimage-class-updater c)
     (string-append c " bw-updated-cardtable-cardimage"))
 
+  ; precompute wikiurl regex for efficency
+  (define wikiurl-regex (pregexp (format "^https://(~a)\\.fandom\\.com(/wiki/.*)$" px-wikiname)))
+
   (define attributes-updater
     (compose1
      ; uncollapsing
@@ -107,12 +110,15 @@
               (λ (class) (string-join (classlist-updater (string-split class " ")) " ")))
      (curry attribute-maybe-update 'class class-updater)
      ; change links to stay on the same wiki
-     (curry attribute-maybe-update 'href
-            (λ (href)
-              ((compose1
-                (λ (href) (regexp-replace #rx"^(/wiki/.*)" href (format "/~a\\1" wikiname)))
-                (λ (href) (regexp-replace (pregexp (format "^https://(~a)\\.fandom\\.com(/wiki/.*)" px-wikiname)) href "/\\1\\2")))
-               href)))
+     (let
+       ; precompute wikiname replacement pattern
+       ([wiki-substitution (format "/~a\\1" wikiname)])
+       (curry attribute-maybe-update 'href
+              (λ (href)
+                ((compose1
+                  (λ (href) (regexp-replace #rx"^(/wiki/.*)$" href wiki-substitution))
+                  (λ (href) (regexp-replace wikiurl-regex href "/\\1\\2")))
+                 href))))
      ; add noreferrer to a.image
      (curry u
             (λ (v) (and #;(eq? element-type 'a)