diff --git a/main.scm b/main.scm
index d831c92..70961e0 100755
--- a/main.scm
+++ b/main.scm
@@ -105,18 +105,21 @@
     (h5        . ,enumerate-tag)
     ;; if adjust-relative is true, all relative links should get prefixed with
     ;; the relative-root.
-    ,(if adjust-relative
-         `(a .
-           ,(lambda (t i)
-              `(,t .
-                ,(alist-update
-                  '@
-                  (alist-update
-                   'href
-                   `(,adjust-relative ,(alist-ref 'href (alist-ref '@ i)))
-                   (alist-ref '@ i))
-                  i))))
-         `(a . ,(lambda (t i) `(,t . ,i))))
+    `(a .
+      ,(lambda (t i)
+         (let ((linkurl (alist-ref 'href (alist-ref '@ i))))
+           `(,t .
+             ,(if (and adjust-relative
+                       (not (string-prefix? "/" linkurl))
+                       (not (string-prefix? "https://" linkurl))
+                       (not (string-prefix? "http://" linkurl))
+                       (not (string-prefix? "mailto:" linkurl))
+                       (not (string-prefix? "https://" linkurl)))
+
+                  (alist-update '@
+                   (alist-update 'href `(,adjust-relative ,linkurl) (alist-ref '@ i))
+                   i)
+                  i)))))
     ;; this copied from lowdown html-serialization-rules* because it
     ;; is for some reason not exported??
     (*COMMENT* . ,(lambda (_ str) (list #\< "!--" str "--" #\>)))