diff --git a/crates/accelerate/src/sparse_pauli_op.rs b/crates/accelerate/src/sparse_pauli_op.rs
index 4a4836ce69ab..68406bba234e 100644
--- a/crates/accelerate/src/sparse_pauli_op.rs
+++ b/crates/accelerate/src/sparse_pauli_op.rs
@@ -317,6 +317,9 @@ fn decompose_first_level(
             out_stack.push(PauliLocation::new(0, 0, 0));
         }
         _ => {
+            unsafe { scratch.set_len(side * side) };
+            let mut ptr = 0usize;
+
             let cur_qubit = num_qubits - 1;
             let mid = 1 << cur_qubit;
             let loc = PauliLocation::new(0, 0, cur_qubit);
@@ -344,7 +347,8 @@ fn decompose_first_level(
                     let i_col = i_col_0 + off_col;
                     let z_col = z_col_0 + off_col;
                     let value = in_op[[i_row, i_col]] + in_op[[z_row, z_col]];
-                    scratch.push(value);
+                    scratch[ptr] = value;
+                    ptr += 1;
                     i_nonzero = i_nonzero || (value != zero);
                 }
 
@@ -354,7 +358,8 @@ fn decompose_first_level(
                     let x_col = x_col_0 + off_col;
                     let y_col = y_col_0 + off_col;
                     let value = in_op[[x_row, x_col]] + in_op[[y_row, y_col]];
-                    scratch.push(value);
+                    scratch[ptr] = value;
+                    ptr += 1;
                     x_nonzero = x_nonzero || (value != zero);
                 }
             }
@@ -365,7 +370,8 @@ fn decompose_first_level(
                     let x_col = x_col_0 + off_col;
                     let y_col = y_col_0 + off_col;
                     let value = in_op[[x_row, x_col]] - in_op[[y_row, y_col]];
-                    scratch.push(value);
+                    scratch[ptr] = value;
+                    ptr += 1;
                     y_nonzero = y_nonzero || (value != zero);
                 }
                 let i_row = i_row_0 + off_row;
@@ -374,7 +380,8 @@ fn decompose_first_level(
                     let i_col = i_col_0 + off_col;
                     let z_col = z_col_0 + off_col;
                     let value = in_op[[i_row, i_col]] - in_op[[z_row, z_col]];
-                    scratch.push(value);
+                    scratch[ptr] = value;
+                    ptr += 1;
                     z_nonzero = z_nonzero || (value != zero);
                 }
             }