diff --git a/sumcheck/src/prover.rs b/sumcheck/src/prover.rs
index 69055f242..ff909c72d 100644
--- a/sumcheck/src/prover.rs
+++ b/sumcheck/src/prover.rs
@@ -541,15 +541,21 @@ impl<'a, E: ExtensionField> IOPProverState<'a, E> {
                 .flattened_ml_extensions
                 .par_iter_mut()
                 .for_each(|mle| {
-                    if let Some(mle) = Arc::get_mut(mle) {
+                    if num_variables == 1 {
+                        // first time fix variable should be create new instance
                         if mle.num_vars() > 0 {
-                            mle.fix_variables_in_place(&[p.elements])
+                            *mle = mle.fix_variables(&[p.elements]).into();
+                        } else {
+                            *mle = Arc::new(DenseMultilinearExtension::from_evaluation_vec_smart(
+                                0,
+                                mle.get_base_field_vec().to_vec(),
+                            ))
                         }
                     } else {
-                        *mle = Arc::new(DenseMultilinearExtension::from_evaluation_vec_smart(
-                            0,
-                            mle.get_base_field_vec().to_vec(),
-                        ))
+                        let mle = Arc::get_mut(mle).unwrap();
+                        if mle.num_vars() > 0 {
+                            mle.fix_variables_in_place(&[p.elements]);
+                        }
                     }
                 });
         };
diff --git a/sumcheck/src/test.rs b/sumcheck/src/test.rs
index 78eb4de4f..12eb93374 100644
--- a/sumcheck/src/test.rs
+++ b/sumcheck/src/test.rs
@@ -4,7 +4,7 @@ use ark_std::{rand::RngCore, test_rng};
 use ff::Field;
 use ff_ext::ExtensionField;
 use goldilocks::GoldilocksExt2;
-use multilinear_extensions::virtual_poly::VirtualPolynomial;
+use multilinear_extensions::{mle::DenseMultilinearExtension, virtual_poly::VirtualPolynomial};
 use rayon::iter::{IntoParallelRefMutIterator, ParallelIterator};
 use transcript::{BasicTranscript, Transcript};
 
@@ -81,9 +81,22 @@ fn test_sumcheck_internal<E: ExtensionField>(
             .flattened_ml_extensions
             .par_iter_mut()
             .for_each(|mle| {
-                Arc::get_mut(mle)
-                    .unwrap()
-                    .fix_variables_in_place(&[p.elements]);
+                if num_variables == 1 {
+                    // first time fix variable should be create new instance
+                    if mle.num_vars() > 0 {
+                        *mle = mle.fix_variables(&[p.elements]).into();
+                    } else {
+                        *mle = Arc::new(DenseMultilinearExtension::from_evaluation_vec_smart(
+                            0,
+                            mle.get_base_field_vec().to_vec(),
+                        ))
+                    }
+                } else {
+                    let mle = Arc::get_mut(mle).unwrap();
+                    if mle.num_vars() > 0 {
+                        mle.fix_variables_in_place(&[p.elements]);
+                    }
+                }
             });
     };
     let subclaim = IOPVerifierState::check_and_generate_subclaim(&verifier_state, &asserted_sum);