diff --git a/ortools/sat/python/cp_model.py b/ortools/sat/python/cp_model.py
index 2d852a919b..5999c76cf6 100644
--- a/ortools/sat/python/cp_model.py
+++ b/ortools/sat/python/cp_model.py
@@ -3522,8 +3522,8 @@ def value(self, expression: LinearExprT) -> int:
         if not self.has_response():
             raise RuntimeError("solve() has not been called.")
 
-        value = 0
-        to_process = [(expression, 1)]
+        value: int = 0
+        to_process: list[tuple[LinearExprT, int]] = [(expression, 1)]
         while to_process:
             expr, coeff = to_process.pop()
             if isinstance(expr, IntegralTypes):
diff --git a/ortools/sat/python/cp_model_test.py b/ortools/sat/python/cp_model_test.py
index 5f76bd952f..a99b7a58ac 100644
--- a/ortools/sat/python/cp_model_test.py
+++ b/ortools/sat/python/cp_model_test.py
@@ -32,7 +32,7 @@ def on_solution_callback(self) -> None:
         self.__solution_count += 1
 
     @property
-    def solution_count(self) -> None:
+    def solution_count(self) -> int:
         return self.__solution_count
 
 
@@ -57,13 +57,13 @@ class SolutionObjective(cp_model.CpSolverSolutionCallback):
 
     def __init__(self) -> None:
         cp_model.CpSolverSolutionCallback.__init__(self)
-        self.__obj = 0
+        self.__obj: float = 0
 
     def on_solution_callback(self) -> None:
         self.__obj = self.objective_value
 
     @property
-    def obj(self) -> None:
+    def obj(self) -> float:
         return self.__obj
 
 
@@ -88,11 +88,11 @@ def on_solution_callback(self) -> None:
             self.__bool_var_values.append(self.boolean_value(bool_var))
 
     @property
-    def int_var_values(self) -> None:
+    def int_var_values(self) -> list[int]:
         return self.__int_var_values
 
     @property
-    def bool_var_values(self) -> None:
+    def bool_var_values(self) -> list[bool]:
         return self.__bool_var_values
 
 
@@ -647,7 +647,10 @@ def testCircuit(self) -> None:
         print("testCircuit")
         model = cp_model.CpModel()
         x = [model.new_bool_var(f"x{i}") for i in range(5)]
-        model.add_circuit((i, i + 1, x[i]) for i in range(5))
+        arcs: list[tuple[int, int, cp_model.LiteralT]] = [
+            (i, i + 1, x[i]) for i in range(5)
+        ]
+        model.add_circuit(arcs)
         self.assertLen(model.proto.variables, 5)
         self.assertLen(model.proto.constraints, 1)
         self.assertLen(model.proto.constraints[0].circuit.heads, 5)
@@ -659,7 +662,10 @@ def testMultipleCircuit(self) -> None:
         print("testMultipleCircuit")
         model = cp_model.CpModel()
         x = [model.new_bool_var(f"x{i}") for i in range(5)]
-        model.add_multiple_circuit((i, i + 1, x[i]) for i in range(5))
+        arcs: list[tuple[int, int, cp_model.LiteralT]] = [
+            (i, i + 1, x[i]) for i in range(5)
+        ]
+        model.add_multiple_circuit(arcs)
         self.assertLen(model.proto.variables, 5)
         self.assertLen(model.proto.constraints, 1)
         self.assertLen(model.proto.constraints[0].routes.heads, 5)