diff --git a/src/Deriving/OpenApi.hs b/src/Deriving/OpenApi.hs
index 41ee075..463655a 100644
--- a/src/Deriving/OpenApi.hs
+++ b/src/Deriving/OpenApi.hs
@@ -40,6 +40,7 @@ import Control.Lens
 import qualified Data.Aeson.Types as A
 import Data.OpenApi
 import Data.OpenApi.Internal.Schema
+import Data.OpenApi.Internal.ParamSchema
 import Data.Proxy
 import Data.Typeable
 import Deriving.Aeson
@@ -77,6 +78,13 @@ instance
     openApiSchemaModifier @xs
       <$> genericDeclareNamedSchema (openApiOptionsModifier @xs defaultSchemaOptions) (Proxy @x)
 
+instance
+  (OpenApiOptionModifier xs, GToParamSchema (Rep x), Generic x) =>
+  ToParamSchema (CustomJSON (xs :: k) x)
+  where
+  toParamSchema Proxy =
+      genericToParamSchema (openApiOptionsModifier @xs defaultSchemaOptions) (Proxy @x)
+
 class OpenApiOptionModifier x where
   openApiOptionsModifier :: SchemaOptions -> SchemaOptions
   openApiOptionsModifier = id