@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics;
 using System.Runtime.InteropServices;
 
 namespace Python.Runtime
@@ -85,6 +86,7 @@ internal static CLRObject Restore(object ob, IntPtr pyHandle, InterDomainContext
                 pyHandle = pyHandle,
                 tpHandle = Runtime.PyObject_TYPE(pyHandle)
             };
+            Debug.Assert(co.tpHandle != IntPtr.Zero);
             co.Load(context);
             return co;
         }
 
@@ -85,9 +85,11 @@ internal static void Use(ITypeOffsets offsets)
         internal static Dictionary<string, int> GetOffsets()
         {
             var properties = typeof(TypeOffset).GetProperties(FieldFlags);
-            return properties.ToDictionary(
-                    keySelector: p => p.Name,
-                    elementSelector: p => (int)p.GetValue(obj: null, index: null));
+            var result = properties.ToDictionary(
+                            keySelector: p => p.Name,
+                            elementSelector: p => (int)p.GetValue(obj: null, index: null));
+            Debug.Assert(result.Values.Any(v => v != 0));
+            return result;
         }
 
         internal static int GetOffsetUncached(string name)
Original file line number	Diff line number	Diff line change
@@ -85,9 +85,11 @@ internal static void Use(ITypeOffsets offsets)
85	85	internal static Dictionary<string, int> GetOffsets()
86	86	{
87	87	var properties = typeof(TypeOffset).GetProperties(FieldFlags);
88		- return properties.ToDictionary(
89		- keySelector: p => p.Name,
90		- elementSelector: p => (int)p.GetValue(obj: null, index: null));
	88	+ var result = properties.ToDictionary(
	89	+ keySelector: p => p.Name,
	90	+ elementSelector: p => (int)p.GetValue(obj: null, index: null));
	91	+ Debug.Assert(result.Values.Any(v => v != 0));
	92	+ return result;
91	93	}
92	94
93	95	internal static int GetOffsetUncached(string name)