diff --git a/qiskit_optimization/problems/quadratic_expression.py b/qiskit_optimization/problems/quadratic_expression.py
index 460fdff9..c6a7b8a7 100644
--- a/qiskit_optimization/problems/quadratic_expression.py
+++ b/qiskit_optimization/problems/quadratic_expression.py
@@ -109,7 +109,7 @@ def _coeffs_to_dok_matrix(
 
             # Check if the python version is at least 3.9.
             # See pull request #594 for more details why we do this check.
-            new_update_rule = sys.version_info >= (3,9)
+            new_update_rule = sys.version_info >= (3, 9)
 
             n = self.quadratic_program.get_num_vars()
             coeffs = dok_matrix((n, n))