diff --git a/nixos/modules/tasks/network-interfaces.nix b/nixos/modules/tasks/network-interfaces.nix
index 868039177d87..97b37b0714cd 100644
--- a/nixos/modules/tasks/network-interfaces.nix
+++ b/nixos/modules/tasks/network-interfaces.nix
@@ -108,7 +108,7 @@ let
         '';
       };
 
-      ipv6prefixLength = mkOption {
+      ipv6PrefixLength = mkOption {
         default = 64;
         example = 64;
         type = types.int;