diff --git a/qiskit_aer/primitives/estimator.py b/qiskit_aer/primitives/estimator.py
index 17bdfa7ba1..a337567ea4 100644
--- a/qiskit_aer/primitives/estimator.py
+++ b/qiskit_aer/primitives/estimator.py
@@ -126,7 +126,7 @@ def __init__(
 
     @property
     @deprecate_func(
-        since=0.13,
+        since="0.13",
         package_name="qiskit-aer",
         is_property=True,
     )
@@ -136,7 +136,7 @@ def approximation(self):
 
     @approximation.setter
     @deprecate_func(
-        since=0.13,
+        since="0.13",
         package_name="qiskit-aer",
         is_property=True,
     )