diff --git a/modules/platform/hetzner.nix b/modules/platform/hetzner.nix
index 29a9355..a51b916 100644
--- a/modules/platform/hetzner.nix
+++ b/modules/platform/hetzner.nix
@@ -9,7 +9,7 @@ in
       default = false;
     };
     ipv4Address = lib.mkOption {
-      type = with lib.types; nullOr (strMatching "^[0-9a-zA-Z:]+/32$");
+      type = with lib.types; nullOr (strMatching "^[0-9]+.[0-9]+.[0-9]+.[0-9]+/32$");
       default = null;
     };
     ipv6Address = lib.mkOption {