diff --git a/qiskit/circuit/library/standard_gates/multi_control_rotation_gates.py b/qiskit/circuit/library/standard_gates/multi_control_rotation_gates.py
index 38c0d581e8a9..95e7cadd023a 100644
--- a/qiskit/circuit/library/standard_gates/multi_control_rotation_gates.py
+++ b/qiskit/circuit/library/standard_gates/multi_control_rotation_gates.py
@@ -115,8 +115,9 @@ def mcsu2_real_diagonal(
     if unitary.shape != (2, 2):
         raise QiskitError("parameter unitary in mcsu2_real_diagonal must be a 2x2 matrix")
 
-    is_main_diag_real = np.isreal(np.real_if_close(unitary).diagonal()).all()
-    is_secondary_diag_real = np.isreal(np.real_if_close(np.fliplr(unitary)).diagonal()).all()
+    unitary = np.real_if_close(unitary)
+    is_main_diag_real = np.isreal(unitary.diagonal()).all()
+    is_secondary_diag_real = np.isreal(np.fliplr(unitary).diagonal()).all()
 
     if not is_main_diag_real and not is_secondary_diag_real:
         raise QiskitError("parameter unitary in mcsu2_real_diagonal must have one real diagonal")