diff --git a/nixos/doc/manual/development/option-declarations.xml b/nixos/doc/manual/development/option-declarations.xml
index cab721f2e555..d62d0896bb7c 100644
--- a/nixos/doc/manual/development/option-declarations.xml
+++ b/nixos/doc/manual/development/option-declarations.xml
@@ -135,8 +135,8 @@ services.xserver.displayManager.enable = mkOption {
   type = with types; nullOr (enum [ "slim" ]);
 };</screen></example>
 
-<example xml:id='ex-option-declaration-eot-backend-sdm'><title>Extending
-    <literal>services.foo.backend</literal> in the <literal>sdm</literal>
+<example xml:id='ex-option-declaration-eot-backend-sddm'><title>Extending
+    <literal>services.foo.backend</literal> in the <literal>sddm</literal>
     module</title>
 <screen>
 services.xserver.displayManager.enable = mkOption {