diff --git a/doc/functions/library/attrsets.xml b/doc/functions/library/attrsets.xml
index 3c5823c25891..f3ceeac0e888 100644
--- a/doc/functions/library/attrsets.xml
+++ b/doc/functions/library/attrsets.xml
@@ -772,7 +772,7 @@ nameValuePair "some" 6
    <title>Modifying each value of an attribute set</title>
 <programlisting><![CDATA[
 lib.attrsets.mapAttrs
-  (name: value: name + "-" value)
+  (name: value: name + "-" + value)
   { x = "foo"; y = "bar"; }
 => { x = "x-foo"; y = "y-bar"; }
 ]]></programlisting>