diff --git a/nixos/modules/services/security/oauth2_proxy.nix b/nixos/modules/services/security/oauth2_proxy.nix
index 486f3ab0538..77c579279ab 100644
--- a/nixos/modules/services/security/oauth2_proxy.nix
+++ b/nixos/modules/services/security/oauth2_proxy.nix
@@ -538,6 +538,7 @@ in
 
     extraConfig = mkOption {
       default = {};
+      type = types.attrsOf types.anything;
       description = ''
         Extra config to pass to oauth2-proxy.
       '';