diff --git a/smt/utils/kriging.py b/smt/utils/kriging.py
index 753324d5f..4f6179c9e 100644
--- a/smt/utils/kriging.py
+++ b/smt/utils/kriging.py
@@ -1550,7 +1550,7 @@ def quadratic(x):
     return f
 
 
-@njit_use(parallel=True)
+@njit_use(parallel=False)
 def matrix_data_corr_levels_cat_matrix(
     i, n_levels, theta_cat, theta_bounds, is_ehh: bool
 ):
@@ -1563,9 +1563,8 @@ def matrix_data_corr_levels_cat_matrix(
             if j == k + j:
                 Theta_mat[j, k + j] = 1.0
             else:
-                val = theta_cat[int(v)]
-                Theta_mat[int(j), int(k + j)] = val
-                Theta_mat[int(k + j), int(j)] = val
+                Theta_mat[j, k + j] = theta_cat[int(v)]
+                Theta_mat[k + j, j] = theta_cat[int(v)]
                 v = v + 1
 
     for j in range(n_levels[i]):