diff --git a/halo2-base/src/gates/builder/mod.rs b/halo2-base/src/gates/builder/mod.rs
index f70def08..155ab4ad 100644
--- a/halo2-base/src/gates/builder/mod.rs
+++ b/halo2-base/src/gates/builder/mod.rs
@@ -627,7 +627,9 @@ impl<F: ScalarField> RangeCircuitBuilder<F> {
     /// Auto-configures the circuit configuration parameters. Mutates the configuration parameters of the circuit
     /// and also returns a copy of the new configuration.
     pub fn config(&mut self, minimum_rows: Option<usize>) -> BaseConfigParams {
+        let lookup_bits = self.0.config_params.lookup_bits;
         self.0.config_params = self.0.builder.borrow().config(self.0.config_params.k, minimum_rows);
+        self.0.config_params.lookup_bits = lookup_bits;
         self.0.config_params.clone()
     }
 }