diff --git a/lib/tests/misc.nix b/lib/tests/misc.nix
index 3f2d742e788..cf99aca58c0 100644
--- a/lib/tests/misc.nix
+++ b/lib/tests/misc.nix
@@ -213,6 +213,30 @@ runTests {
   };
 
 
+# ATTRSETS
+
+  # code from the example
+  testRecursiveUpdateUntil = {
+    expr = recursiveUpdateUntil (path: l: r: path == ["foo"]) {
+      # first attribute set
+      foo.bar = 1;
+      foo.baz = 2;
+      bar = 3;
+    } {
+      #second attribute set
+      foo.bar = 1;
+      foo.quz = 2;
+      baz = 4;
+    };
+    expected = {
+      foo.bar = 1; # 'foo.*' from the second set
+      foo.quz = 2; #
+      bar = 3;     # 'bar' from the first set
+      baz = 4;     # 'baz' from the second set
+    };
+  };
+
+
 # GENERATORS
 # these tests assume attributes are converted to lists
 # in alphabetical order
diff --git a/nixos/doc/manual/release-notes/rl-1809.xml b/nixos/doc/manual/release-notes/rl-1809.xml
index d527984f5ef..d831f851446 100644
--- a/nixos/doc/manual/release-notes/rl-1809.xml
+++ b/nixos/doc/manual/release-notes/rl-1809.xml
@@ -278,6 +278,8 @@ inherit (pkgs.nixos {
      <literal>lib.traceCallXml</literal> has been deprecated. Please complain
      if you use the function regularly.
     </para>
+   </listitem>
+   <listitem>
     <para>
      The attribute <literal>lib.nixpkgsVersion</literal> has been deprecated in
      favor of <literal>lib.version</literal>. Please refer to the discussion in
@@ -285,6 +287,13 @@ inherit (pkgs.nixos {
      for further reference.
     </para>
    </listitem>
+   <listitem>
+    <para>
+     <literal>lib.recursiveUpdateUntil</literal> was not acting according to its
+     specification. It has been fixed to act according to the docstring, and a
+     test has been added.
+    </para>
+   </listitem>
    <listitem>
     <para>
      The module for <option>security.dhparams</option> has two new options now: