diff --git a/transform/absurl.go b/transform/absurl.go
index 1a98a592c..255ac33b6 100644
--- a/transform/absurl.go
+++ b/transform/absurl.go
@@ -13,12 +13,16 @@
 
 package transform
 
-var ar *absURLReplacer = newAbsURLReplacer()
+var ar = newAbsURLReplacer()
 
+// AbsURL replaces relative URLs with absolute ones
+// in HTML files, using the baseURL setting.
 var AbsURL = func(ct contentTransformer) {
 	ar.replaceInHTML(ct)
 }
 
+// AbsURLInXML replaces relative URLs with absolute ones
+// in XML files, using the baseURL setting.
 var AbsURLInXML = func(ct contentTransformer) {
 	ar.replaceInXML(ct)
 }