diff --git a/halo2-base/src/utils/halo2.rs b/halo2-base/src/utils/halo2.rs
index f945971d..50b5fc7e 100644
--- a/halo2-base/src/utils/halo2.rs
+++ b/halo2-base/src/utils/halo2.rs
@@ -118,6 +118,6 @@ pub fn constrain_virtual_equals_external<F: Field + Ord>(
 
 /// Circuit with default values.
 pub trait CircuitWithDefault<F: Field>: Circuit<F> {
-    /// Return Circuit with default inputs for the given params.
-    fn default(witness_gen_only: bool, params: Self::Params) -> Self;
+    /// Return Circuit with default inputs for the given params. Return struct could be used for pkey generation.
+    fn default(params: Self::Params) -> Self;
 }