pythonnet · filmor · Feb 26, 2020 · Feb 26, 2020
diff --git a/src/runtime/Util.cs b/src/runtime/Util.cs
@@ -3,7 +3,7 @@

 namespace Python.Runtime
 {
-    internal class Util
+    internal static class Util
    {
        internal static Int64 ReadCLong(IntPtr tp, int offset)
        {
@@ -29,5 +29,12 @@ internal static void WriteCLong(IntPtr type, int offset, Int64 flags)
                Marshal.WriteInt64(type, offset, flags);
            }
        }
+
+        /// <summary>
+        /// Null-coalesce: if <paramref name="primary"/> parameter is not
+        /// <see cref="IntPtr.Zero"/>, return it. Otherwise return <paramref name="fallback"/>.
+        /// </summary>
+        internal static IntPtr Coalesce(this IntPtr primary, IntPtr fallback)
+            => primary == IntPtr.Zero ? fallback : primary;
    }
-}
+}
diff --git a/src/runtime/pythonengine.cs b/src/runtime/pythonengine.cs
@@ -758,11 +758,14 @@ public static void With(PyObject obj, Action<dynamic> Body)
            catch (PythonException e)
            {
                ex = e;
-                type = ex.PyType;
-                val = ex.PyValue;
-                traceBack = ex.PyTB;
+                type = ex.PyType.Coalesce(type);
+                val = ex.PyValue.Coalesce(val);
+                traceBack = ex.PyTB.Coalesce(traceBack);
            }

+            Runtime.XIncref(type);
+            Runtime.XIncref(val);
+            Runtime.XIncref(traceBack);
            var exitResult = obj.InvokeMethod("__exit__", new PyObject(type), new PyObject(val), new PyObject(traceBack));

            if (ex != null && !exitResult.IsTrue()) throw ex;