diff --git a/src/embed_tests/TestRuntime.cs b/src/embed_tests/TestRuntime.cs
index 32369190c..4e05850c1 100644
--- a/src/embed_tests/TestRuntime.cs
+++ b/src/embed_tests/TestRuntime.cs
@@ -92,27 +92,29 @@ public static void PyCheck_Iter_PyObject_IsIterable_ThreadingLock_Test()
         {
             Runtime.Runtime.Py_Initialize();
 
-            // Create an instance of threading.Lock, which is one of the very few types that does not have the
-            // TypeFlags.HaveIter set in Python 2. This tests a different code path in PyObject_IsIterable and PyIter_Check.
-            var threading = Runtime.Runtime.PyImport_ImportModule("threading");
-            Exceptions.ErrorCheck(threading);
-            var threadingDict = Runtime.Runtime.PyModule_GetDict(threading);
-            Exceptions.ErrorCheck(threadingDict);
-            var lockType = Runtime.Runtime.PyDict_GetItemString(threadingDict, "Lock");
-            if (lockType.IsNull)
-                throw new KeyNotFoundException("class 'Lock' was not found in 'threading'");
-
-            var args = Runtime.Runtime.PyTuple_New(0);
-            var lockInstance = Runtime.Runtime.PyObject_CallObject(lockType.DangerousGetAddress(), args);
-            Runtime.Runtime.XDecref(args);
-            Exceptions.ErrorCheck(lockInstance);
-
-            Assert.IsFalse(Runtime.Runtime.PyObject_IsIterable(lockInstance));
-            Assert.IsFalse(Runtime.Runtime.PyIter_Check(lockInstance));
-
-            threading.Dispose();
-
-            Runtime.Runtime.Py_Finalize();
+            try
+            {
+                // Create an instance of threading.Lock, which is one of the very few types that does not have the
+                // TypeFlags.HaveIter set in Python 2. This tests a different code path in PyObject_IsIterable and PyIter_Check.
+                using var threading = Runtime.Runtime.PyImport_ImportModule("threading");
+                Exceptions.ErrorCheck(threading);
+                var threadingDict = Runtime.Runtime.PyModule_GetDict(threading);
+                Exceptions.ErrorCheck(threadingDict);
+                var lockType = Runtime.Runtime.PyDict_GetItemString(threadingDict, "Lock");
+                if (lockType.IsNull)
+                    throw new PythonException();
+
+                using var args = NewReference.DangerousFromPointer(Runtime.Runtime.PyTuple_New(0));
+                using var lockInstance = Runtime.Runtime.PyObject_CallObject(lockType, args);
+                Exceptions.ErrorCheck(lockInstance);
+
+                Assert.IsFalse(Runtime.Runtime.PyObject_IsIterable(lockInstance));
+                Assert.IsFalse(Runtime.Runtime.PyIter_Check(lockInstance));
+            }
+            finally
+            {
+                Runtime.Runtime.Py_Finalize();
+            }
         }
     }
 }
diff --git a/src/runtime/runtime.cs b/src/runtime/runtime.cs
index 6ebf885a0..232dd8708 100644
--- a/src/runtime/runtime.cs
+++ b/src/runtime/runtime.cs
@@ -1009,6 +1009,11 @@ internal static string PyObject_GetTypeName(IntPtr op)
             return Marshal.PtrToStringAnsi(ppName);
         }
 
+        /// <summary>
+        /// Test whether the Python object is an iterable.
+        /// </summary>
+        internal static bool PyObject_IsIterable(BorrowedReference ob)
+            => PyObject_IsIterable(ob.DangerousGetAddress());
         /// <summary>
         /// Test whether the Python object is an iterable.
         /// </summary>
@@ -1078,7 +1083,10 @@ internal static IntPtr PyObject_GetAttr(IntPtr pointer, IntPtr name)
         internal static IntPtr PyObject_Call(IntPtr pointer, IntPtr args, IntPtr kw) => Delegates.PyObject_Call(pointer, args, kw);
 
 
-        internal static IntPtr PyObject_CallObject(IntPtr pointer, IntPtr args) => Delegates.PyObject_CallObject(pointer, args);
+        internal static NewReference PyObject_CallObject(BorrowedReference callable, BorrowedReference args) => Delegates.PyObject_CallObject(callable, args);
+        internal static IntPtr PyObject_CallObject(IntPtr pointer, IntPtr args)
+            => Delegates.PyObject_CallObject(new BorrowedReference(pointer), new BorrowedReference(args))
+                .DangerousMoveToPointerOrNull();
 
 
         internal static int PyObject_RichCompareBool(IntPtr value1, IntPtr value2, int opid) => Delegates.PyObject_RichCompareBool(value1, value2, opid);
@@ -1880,6 +1888,7 @@ internal static IntPtr PyTuple_GetSlice(IntPtr pointer, long start, long end)
         //====================================================================
         // Python iterator API
         //====================================================================
+        internal static bool PyIter_Check(BorrowedReference ob) => PyIter_Check(ob.DangerousGetAddress());
 
         internal static bool PyIter_Check(IntPtr pointer)
         {
@@ -2317,7 +2326,7 @@ static Delegates()
                 PyObject_DelItem = (delegate* unmanaged[Cdecl]<IntPtr, IntPtr, int>)GetFunctionByName(nameof(PyObject_DelItem), GetUnmanagedDll(_PythonDll));
                 PyObject_GetIter = (delegate* unmanaged[Cdecl]<IntPtr, IntPtr>)GetFunctionByName(nameof(PyObject_GetIter), GetUnmanagedDll(_PythonDll));
                 PyObject_Call = (delegate* unmanaged[Cdecl]<IntPtr, IntPtr, IntPtr, IntPtr>)GetFunctionByName(nameof(PyObject_Call), GetUnmanagedDll(_PythonDll));
-                PyObject_CallObject = (delegate* unmanaged[Cdecl]<IntPtr, IntPtr, IntPtr>)GetFunctionByName(nameof(PyObject_CallObject), GetUnmanagedDll(_PythonDll));
+                PyObject_CallObject = (delegate* unmanaged[Cdecl]<BorrowedReference, BorrowedReference, NewReference>)GetFunctionByName(nameof(PyObject_CallObject), GetUnmanagedDll(_PythonDll));
                 PyObject_RichCompareBool = (delegate* unmanaged[Cdecl]<IntPtr, IntPtr, int, int>)GetFunctionByName(nameof(PyObject_RichCompareBool), GetUnmanagedDll(_PythonDll));
                 PyObject_IsInstance = (delegate* unmanaged[Cdecl]<IntPtr, IntPtr, int>)GetFunctionByName(nameof(PyObject_IsInstance), GetUnmanagedDll(_PythonDll));
                 PyObject_IsSubclass = (delegate* unmanaged[Cdecl]<BorrowedReference, BorrowedReference, int>)GetFunctionByName(nameof(PyObject_IsSubclass), GetUnmanagedDll(_PythonDll));
@@ -2616,7 +2625,7 @@ static Delegates()
             internal static delegate* unmanaged[Cdecl]<IntPtr, IntPtr, int> PyObject_DelItem { get; }
             internal static delegate* unmanaged[Cdecl]<IntPtr, IntPtr> PyObject_GetIter { get; }
             internal static delegate* unmanaged[Cdecl]<IntPtr, IntPtr, IntPtr, IntPtr> PyObject_Call { get; }
-            internal static delegate* unmanaged[Cdecl]<IntPtr, IntPtr, IntPtr> PyObject_CallObject { get; }
+            internal static delegate* unmanaged[Cdecl]<BorrowedReference, BorrowedReference, NewReference> PyObject_CallObject { get; }
             internal static delegate* unmanaged[Cdecl]<IntPtr, IntPtr, int, int> PyObject_RichCompareBool { get; }
             internal static delegate* unmanaged[Cdecl]<IntPtr, IntPtr, int> PyObject_IsInstance { get; }
             internal static delegate* unmanaged[Cdecl]<BorrowedReference, BorrowedReference, int> PyObject_IsSubclass { get; }