diff --git a/nixos/modules/services/networking/wireguard.nix b/nixos/modules/services/networking/wireguard.nix
index dd3cb1af271..adbbc5fc05a 100644
--- a/nixos/modules/services/networking/wireguard.nix
+++ b/nixos/modules/services/networking/wireguard.nix
@@ -301,8 +301,16 @@ in
 
     networking.wireguard = {
 
+      enable = mkOption {
+        description = "Whether to enable WireGuard.";
+        type = types.bool;
+        # 2019-05-25: Backwards compatibility.
+        default = cfg.interfaces != {};
+        example = true;
+      };
+
       interfaces = mkOption {
-        description = "Wireguard interfaces.";
+        description = "WireGuard interfaces.";
         default = {};
         example = {
           wg0 = {
@@ -325,7 +333,7 @@ in
 
   ###### implementation
 
-  config = mkIf (cfg.interfaces != {}) {
+  config = mkIf cfg.enable {
 
     assertions = (attrValues (
         mapAttrs (name: value: {